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FOLWELL    #    WATER    SUPPLY  ? 

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WORKS  OF 
PROF.  A.  PRESCOTT  EOLWELL 


PUBLISHED    BY 


JOHN   WILEY   &   SONS. 


Sewerage. 

The  Designing,  Construction,  and  Maintenance 
of  Sewerage  Systems.    8vo,  cloth,  $3.00. 

Water-Bupply  Engineering. 

The  Designing,  Construction,  and  Maintenance 
of  Water-supply  Systems,  both  City  and  Irriga- 
tion.   8vo,  cloth,  $4.00. 


Water-supply  Engineering. 


THE  DESIGNING,  CONSTRUCTION,  AND  MAIN- 
TENANCE OF  WATER-SUPPLY  SYSTEMS, 
BOTH   CITY  AND   IRRIGATION. 


BY 

A.    PRESCOTT   FOLWELL, 

Member  of  the  A  merican  Society  of  Civil  Engineers  ; 

Member  o;  the  New  England  Water-Works  Association; 

Member  of  the  American  Society  of  Municipal  Improvements  ; 

Associate  Professor  of  Municipal  Engineering,  Lafayette  College. 


SECOND    EDITION,    REVISED    AND    ENLARGED. 
FIRST    THOUSAND, 


NEW  YORK: 

JOHN   WILEY   &   SONS. 

London:    CHAPMAN  &  HALL,  Limited. 
1903. 


Copyright,  1899,  i9°3' 

BY 

A.  PRESCOTT  FOLWELL. 


ROBERT    UKUMMOND,    PRINTER,     NEW    YORK 


\ 


CONTEMTS. 


PART   I.     DESIGNING. 
Chapter  I.     Synopsis. 

AR  r.  FAGH 

1.  Sources  of  Supply i 

2.  Quality  of  Water 2 

;,.   Elements  of  a  System 3 

Chapter  II.     Requisites  of  a  Supply.     Quality. 

4.  Value  of  Water  Analysis 5 

5.  Interpretation  of  Analyses 7 

6.  Inorganic  Matter 11 

7.  Organic  Matter 14 

8.  Physical  Properties 18 

9.  Statistics  of  Disease  in  Relation  to  Drinking-water 20 

10.  Summary.     Requisite  Quality 26 

Chapter  III.     Requisites  of  a  Supply.     Quantity. 

11.  For  Irrigation 29 

12.  Population  to  be  Supplied 30 

13.  Quantity  for  City  and  Suburban  Use 33 

14.  Waste  of  Water 4i 

15.  Water-works  Statistics 44 

16.  Summary.     Quantity  to  be  Provided  for 47 

Chapter  IV.     Sources  of  Supply. 

17.  Rain -, 50 

18.  Surface-water 5i 

19.  Rivers  and  Lakes   53 

20.  Underground  Supplies 53 

21.  Other  Sources 54 

22.  Relative  Use  of  Different  Sources 54 


VI  CONTENTS. 

Chapter  V.     Rainfall. 

ART.  FAGS 

23.  Quality  of  Rain-water 56 

24.  Quantity  of  Rainfall:    Annual 60 

25.  "           "           "       :  Monthly 70 

26.  Gauging  Rainfall 81 

27.  Storage  of  Rain-water 83 

28.  Summary.     Estimating  Future  Rainfall 85 

Chapter  VI.     Surface-water. 

29.  Evaporation 88 

30.  Natural  Storage 94 

31.  Yield,  or  Run-off 98 

32.  Run-off  from  Storms 106 

33.  Storage 109 

34.  Quality  of  Surface-water !•« 

Chapter  VII.     Rivers  and  Lakes. 

35.  Rivers 128 

36.  Quality  of  River-water 130 

37.  Lakes 134 

Chapter  VIII.     Ground-v*^ater. 

38.  Water-bearing  Strata 136 

39.  Classification  of  Ground-waters 140 

40.  Flow  of  Ground-water 143 

41.  Wells 146 

42.  Infiltration-galleries 149 

43.  Springs 151 

44.  Amount  of  Ground-water  Available 152 

45.  Quality  of  Ground-water 155 

Chapter  IX.     Gravity  Systems. 

46.  Definitions 158 

47.  Head-works 158 

48.  Storage-reservoirs  :  Location 160 

49.  "                 "          :  General  Construction 162 

50.  Spillways 166 

51.  Distributing  Reservoirs 169 

52.  Gravity  Supplies  from  Large  Streams 170 

53.  Open  Conduits 171 

54.  Closed  Conduits 182 

55.  Location  of  Conduits 186 

56.  Distribution  Systems  :   Irrigation 187 

57.  "                   "         :   City  Supply 189 


CONTENTS.  VI 1 

Chapter  X.     Pumping  Systems. 

AKT.  PAGE 

58.  Where  Required 197 

59.  General  Design 198 

60.  Intakes  and  Pumping-plants 200 

Chapter   XI.     Hydraulics. 

61.  Statics 206 

62.  Flow  in  Open  Conduits    209 

63.  '       "   Pressure  Conduits 216 

64.  "       "    Hose,  Nozzles,  etc 231 

65.  Measurement  of  Water 234 

Chapter  XII.  Dams  and  Embankments. 

66.  Materials  for  Construction  of  Dams 242 

67.  Masonry  Dams  :  General  Construction 243 

68.  "  "       :   Designing 247 

69.  Rock-fill  Dams 259 

70.  Timber  Dams 263 

71.  Earth   Embankments 268 

72.  Hydraulic  Dam  Construction 277 

73.  Reservoir  Lining 278 

74.  Covered  Reservoirs 283 

Chapter  XIII.     Purification  of  Water. 

75.  General  Principles 287 

76.  Sedimentation 288 

77.  English  Method  of  Filtration 290 

78.  Mechanical   Filters 304 

79.  Other  Purification  Methods 310 

80.  Summary 316 

Chapter  XIV.     Pumping  and  Pumping-engines. 

81.  Pumps 321 

82.  Pumping-engines 327 

83.  Duty  of  Steam  Pumping-engines 331 

84.  Arrangement  of  Pumping-plants 342 

85.  Boilers 352 

86.  Other  Motive  Power  for  Pumps 354 

Chapter  XV.     Designing. 

87.  Collecting  the  Data 364 

88.  Selecting  the  Supply 368 

89.  Tke  General  Design 373 

90.  Details  of  Gravity  Head-works 376 

91.  Pumping-station  and  Inlet  Details 3SS 

92.  Details  of  Ground-water  Plants 393 


VI 11  CONTENTS. 

ART.  PACK 

93.  Details  of  Purification-plants 399 

94.  "        "  Conduits  and  Distribution  Systems 405 

95.  Standpipes 436 

96.  Estimate  of  Cost 445 


PART    II.     CONSTRUCTION. 

Chapter  XVI.     Supervision  and  Measurement  of  Work. 

97.  Reservoirs 453 

98.  Conduits  and  Distribution  Systems 457 

99i   Other  Features 463 

Chapter  XVII.     Practical  Construction. 

100.   Reservoirs 466 

loi.   Distribution  Systems 472 

102.  Wells 479 

PART    III.     MAINTENANCE. 

Chapter  XVIII.     Reservoirs,  Head-works,  and  Intakes. 

103.  Maintaining  Quality  of  Water 485 

104.  "  Quantity  of  Water 488 

105.  Prevention  of  Deterioration  or  Destruction 492 

106.  Intakes,  Wells,  etc 493 

Chapter  XIX.     Pumping-plants  and  Filters. 

107.  Operating  Pumping-plants 49^ 

108.  "  Filters 500 

Chapter  XX.     Pipes  and  Conduits. 

109.  Maintaining  Quality  of  Water 506 

no.  "  Quantity  of  Water 508 

111.  Service-connections  and  Extensions 524 

112.  Prevention  of  Deterioration 527 

Chapter  XXI.     Clerical  and  Commercial. 

11 3.  Keeping  Records 532 

114.  Meters  and  Rates 53^ 

TT5.    Financial    543 

Appendix  A. — Waterworks  Staiistics _ 

Appendix  B.— Hyi>raultcs 550 

Appendix  C— Filtration  Data 552 

Appendix  D. — Practical  Tables 554 

Appendix  E. — Quality  and  Analysis • 555 


ILLUSTRATIONS. 


fLATE  FACK 

I.   Isochlors  for  Massachusetts  and  Connecticut 15 

II.   Typhoid  Death-rates 24 

III.  Population  Curve  for  Baltimore 31 

IV.  Annual     Precipitation    at     Philadelphia,    Vineland,  and    New 

Brunswick 64 

V.    Precipitation  and  Meteorological  Districts  in  the  United  States  65 

VI.   Yield  and  Storage  Diagram;  Sudbury  Watershed 114 

VII.  Temperature  of  a  Lake  that  Freezes 125 

VIII.   Santa  Ana  Canal,  California 175 

IX.   Conduit  on  Trestle 177 

X.    Bench-flume,  Colorado 179 

XI.  Wooden-stave  Pipe 183 

XII.   Coefficient  c  for  New  Cast-iron  Pipe 217 

XIII.  Fire-stream  Diagram 233 

XIV.  Weir-dam  at  Holyoke,  Mass 256 

XV.   Practical  Economic  Profile  of  High  Masonry  Dam 258 

XVI.    Rock-fill  Dams 262 

XVII.   Deep  Well  with  Pump  ;  Strainers 397 

XVIII.   Albany  Filtration-plant 402 

XIX.   Albany  Filtration-plant 404 

FIGURE 

1.  Ground-water  Diversion  by  Inclined  Strata 52 

2.  Rain-gauge 81 

3.  Evaporating-pan 90 

4.  Precipitation  and  Percentage  Collected  ;  Sudbury  Watershed  ....  loi 

5.  Precipitation  and  Percentage  Collected  ;  Sweetwater  Watershed.  loi 

6.  Underground  Flow  in  Stratified  Rock 137 

7.  Underground  Flow  in  Stratified  Rock 138 

8.  Underground  Flow  in  River-basin 138 

9.  Shallow  Wells I39 

10.  Typical  Section  through  Marine  Sedimentary  Deposits 139 

11.  Section  through  Pensacola  Water-bearing  Stratum 142 

12.  Effect  of  Pumping  on  Ground-water 145 

13.  Spring  at  Outcrop 151 

14.  Spring  from  a  Fault 151 

15.  Spring  in  Hardpan 151 

ix 


X  ILL  us TRA  TIONS. 

FIGURE  PAGE 

i6.  Ground-Storage   154 

17.  Distributing-reservoir 160 

18.  Location  of  Mains  and   Gates 192 

19.  Water-pressure  on  an  Inclined  Surface 207 

20.  Centre  of  Pressure  on  a  Trapezoid 208 

21.  Hydraulic  Gradient 225 

22.  Hydraulic  Gradient  ;  Compound  Pipe 226 

23    Water-ram  in  a  2-inch  Pipe 230 

24.  Friction  Loss  in  Fire-hydrants 234 

25.  Dam  on  Timber  Foundation 244 

26.  Rectangular  Dam 249 

27.  Trapezoidal  Dam 250 

28.  Pressure  on  Joint  Normal  to  Resultant 253 

29.  Great  Falls  Dam 265 

30.  Sewell  Falls  Dam 266 

31.  Bear  River  Weir 267 

32.  Butte,  Mont.,  Timber  Dam 267 

33.  Oak  Ridge  Reservoir  Dam 271 

34.  Reservoir  "  -M  "  Dam,  New  York  Water-works 272 

35.  Honey  Lake  Valley  Dam 274 

36.  Puddle-lined  Reservoir 275 

37.  Dam  of  Hydraulic  Construction 278 

38.  Reservoir  Lining  in  Rock  Excavation 2S1 

39.  Covered  Reservoir  ;  Quincy,  111 2S4 

40.  Covered  Reservoir  ;  Wellesley,  Mass 285 

41.  Sections  of  Albany  Filter-beds 299 

42.  Mechanical  Filter 306 

43.  Filter-crib,  Kensington,  Pa 311 

44.  Piston-  and  Plunger-pumps 321 

45.  Bucket-pump 323 

46.  Differential  Plunger 323 

47.  Centrifugal  Pump 325 

48.  Power,  Direct-acting,  and  Fly-wheel  Pumps 328 

49.  Losses  of  Heat  in  a  Steam  Pumping-plant 335 

50.  Triple-expansion  Horizontal  Engine 343 

51.  Vertical  Pumping-enginc 345 

52.  Pump-pit,  Cincinnati  Water-works 348 

53.  Centrifugal  Pump-plant,  Rockford,  111 349 

54.  Setting  of  Return-tubular  Boiler 353 

55.  Air-lift  Pump 361 

56.  Unsuitable  Dam-sites 378 

57.  Reservoir  Cross-section 379 

58.  Estimating  Contents  of  Earth  Dam 381 

59.  Spillway 383 

60.  Cut-off  Flange  for  Pipe 383 

61.  Outlet-pipe  for  Small  Reservoirs 384 


ILL  US  TRA  TIONS.  X 1 

FIGURE  l-AGE 

62.  Gate-house 3S5 

63.  Reservoir  Sluice-gate 3^6 

64.  Head-gates  and  Flushing-out  Sluice 3S8 

65.  Erie  Intake  Crib 391 

66.  Deep  Dug  Wells 398 

67.  Infiltration-crib,  Denver  Water-works 399 

68.  Box-flume  Construction 406 

69.  Stave  and  Binder  Flume 4°? 

70.  Old  Croton  Aqueduct 408 

71.  Sections  of  Concrete  Aqueducts 409 

72.  Joints  of  Cast-iron  Pipes 4" 

73.  Cast-iron  Pipe-specials 414 

74.  Wrought-iron  Pipe 416 

75.  Air-escape  Valve 425 

76.  Bridge-crossings 428 

77.  Fire-hydrant   430 

78.  Hydraulic  Gradient  for  Pumping-main 432 

79.  Distribution  System 433 

€otf.   Elevated  Water-tank 439 

&ob.   Details  of  Elevated  Water-tank 441 

81.  Bottom  of  Standpipe 442 

82.  Contractors  Pipe-and-Special  Map 460 

83.  False  Head  for  Testing  Pipe 462 

84.  Portable  Plank-road 468 

85.  Concreting  Slopes 47o 

86.  Excavation-platform 473 

87.  Pipe-derrick 475 

88.  Yarning-  and  Calking-tools  and  Hammer 478 

89.  Sheathing  Dug  Wells 4S0 

90.  Apparatus  for  Jetting  down  Wells 483 

91.  Temperature  of  Water  in  Mains 506 

92.  Deacon  Waste-water  Meter 510 

93.  Pipe-cutting  Machine 512 

94.  Pipe-scraper 5I5 

95.  Thawing  Pipes  by  Electricity 520 


TABLES. 


PACK 

1.  Density  of  Population,  and  Altitude 33 

2.  Consumption   per  Capita  for  Various  Purposes;  Boston 35 

3.  Consumption  in  Various  Cities  of  the  United  States 36 

4.  Consumption  in  Various  English  Cities 36 

5.  Number  of  Fixtures  in  Use;  Boston 37 

6.  Monthly  Rates  of  Consumption 33 

7.  Maximum  Monthly,  Weekly,  and  Daily  Rates 39 

8.  Number  of  Fire-streams  Required  in  Cities 40 

9.  Persons  per  Dwelling  in  the  United  States 44 

10.  Population  and  Cost  per  Mile  of  Mains 45 

11.  Taps,  Meters,  and  Pipes  in  Various  Cities 45 

12.  Consumption  per  Capita  through  Meters 46 

13.  Analysis  of  Consumption  in  New  England  Cities 47 

14.  Relative  Proportion  of  Cities  using  Each  Source  of  Supply 55 

15.  Analyses  of  Rain-water 57 

16.  Analyses  of  Cistern-water 60 

17.  Normal  Precipitation  in  the  United  States 61 

18.  Annual  Precipitation,  by  Districts  and  Altitudes 62 

19.  Dry  Cycles,  Two-  to  Five-year  Periods 68 

20.  Mean  Monthly  Precipitation 72 

21.  Monthly  Variations  in  Precipitation 74 

22.  Monthly  Precipitation  by  Districts 76 

23.  Mean,  Maximum,  and  Minimum  Monthly  Precipitation 77 

24.  Typical  Dry  Periods 78 

25.  Dryest  Three-  to  Twelve-month  Periods 79 

26.  Maximum  Rates  of  Rainfall 80 

27.  Evaporation  from  Water-surfaces  ;  Annual 89 

28.  Evaporation  from  Water-surfaces  ;  Monthly 89 

29.  Ratios  of  Monthly  to  Annual  Evaporation 91 

30.  Evaporation  from  Grass  and  Earth 92 

31.  Consumption  of  Water  by  Crops 92 

32.  Absorption  Capacity  of  Soils 97 

33.  Average  Percentages  of  Rainfall  Yielded 99 

34.  Yield  of  Connecticut  and  Potomac  Watersheds 100 

35.  Yield  of  Various  Drainage  Areas 102 

36.  Yield  of  New  England  Drainage  Areas,  by  Months 102 

xiii 


XIV  TABLES. 

PAGE 

37.  Temperature  of  Ponds  and  Reservoirs 122 

38.  Temperature  of  Lakes  at  Different  Depths 122 

39.  Organic  Matter  at  Surface  and  Bottom  of  Lakes 123 

40.  Analysis  of  Passaic  River  Water 132 

41.  Varying  Amounts  of  Impurities  in  Rivers 133 

42.  Cities  having  Ground-water  Supplies 147 

43.  Analyses  of  Brooklyn  Driven-well  Water 156 

44.  Some  Great  Irrigation  Canals 182 

45.  Some  Closed  Conduits 186 

46.  c  for  Smooth  Circular  Conduits 210 

47.  c  for  Rectangular  Conduits 211 

48.  Values  of  Backwater  Function 215 

49.  Transporting  Power  of  Currents 216 

50.  Friction  Factors  for  Cast-iron  Pipe 219 

51.  Friction  Factors  for  Smooth  Pipes 220 

52.  Jets  from  Smooth  Nozzles 231 

53.  Friction  Factors  for  Hose 231 

54.  Weight  of  Distilled  Water 235 

55.  c  for  Vertical  Circular  Orifices 236 

56.  c  for  Weirs  With  and  Without  Contractions 239 

57.  Weight  of  Masonry 249 

58.  Coefficients  of  Friction  for  Masonry 250 

59.  Crushing  Strength  of  Stone 251 

60.  Data  of  Masonry  Dams 260 

61.  Data  of  Rock-fill  Dams. 264 

62.  Data  of  Earth  Dams 276 

63.  Rates  of  Filtration  in  European  Cities 295 

64.  Rates  of  Flow  through  Different  Sands 297 

65.  Results  of  Tests  of  Mechanical  Filters 308 

66.  Filtration  and  Sources  of  Supply 318 

67.  Latent  Heat  of  Evaporation 333 

68.  Data  of  High-duty  Pumping-engines 340 

69.  N.  E.  W.  W.  Assn.  Standard  Dimensions  and  Weights  of  Cast-iron 

Water-pipe 412 

70.  Dimensions  of  Pipe-specials , 415 

71.  Economic  Proportions  for  Stave-pipe  Designs 424 

72.  Cost  of  Pumping  in  Twelve  Cities 499 

73.  Typhoid-fever  Death-rates 547 

74.  Population,  Consumption,  Receipts,  Meters,  etc.,  Forty  Cities....  549 

75.  Summary  and  Averages  of  Table  74 550 

76.  Loss  in  Valves 552 

77.  Data  concerning  Sand  Filtration  of  Water  in  America 552 

78.  Areas  of  Pipe  Sections 554 

79.  Velocity  of  Flow  in  Pipes ..  =  ,0 .......  -    . 554. 


WATER-SUPPLY   ENGINEERING. 


PART   I.     DESIGNING. 


CHAPTER   I. 

SYNOPSIS. 

Article  1.     Sources  of  Supply. 

All  mankind,  whether  wandering  savage,  is(>\ated 
pioneer,  or  dweller  in  a  crowded  city,  must  have  water  for 
drinking,  needs  it  for  cleansing  himself  and  his  belongings, 
and  for  irrigation;  and  under  many  circumstances  he  uses  it 
for  power  or  in  manufacturing,  as  well  as  for  extinguishing 
fires,  sprinkling  lawns  and  streets,  flushing  sewers,  and  many 
other  purposes.  The  water  for  all  'these  uses  can  have  but 
one  first  source — the  moisture  i'n  the  atmosphere.  This 
generally  becomes  available  as  rain  (or  snow),  but  dew  is  in 
some  cases  an  important  consideration. 

Water  falling  as  rain  or  snow  may  be  caught  before  reach- 
ing the  ground  and  stored  in  basins  or  cisterns  hewn  from 
the  rock,  dug  in  the  soil,  or  in  the  shape  of  tanks  of  wood  or 
iron.  Or  it  may  be  taken  from  rivers  or  smaller  streams 
direct,  or  these  may  be  intercepted  and  stored  in  large 
artificial  reservoirs,  or  in  natural  reservoirs,  i.e.,  lakes.  Or 
that  which  soaks  into  the  ground  may  be  obtained  by  wells, 


2  WATER-SUPPLY  ENGINEERING. 

shallow  or  deep,  dug  or  driven;  or  at  its  emergence  in  the 
form  of  springs. 

Art.  2.     Quality  of  Water. 

Water  does  not  exist  in  nature  chemically  pure — (H,0) — 
but,  owing  to  its  almost  universal  solvent  powers,  it  contains 
many  foreign  matters  in  solution;  and,  when  flowing  in 
streams  or  lakes,  in  suspension  also.  Many  of  these  matters 
in  solution  are  harmless,  some  are  beneficial,  and  a  few  are 
injurious.  Rain-water  washes  impurities  from  the  air,  river- 
water  receives  much  organic  and  some  mineral  matter  from 
the  surface  flow  or  "run-off"  of  fallen  rain,  and  ground- 
waters absorb  much  mineral  and  some  organic  matter  from 
the  strata  through  which  they  pass.  In  only  exceptional 
cases  are  these  matters  injurious  to  man  before  the  country 
has  been  cleared  and  occupied  by  him.  But  the  enormous 
anrounts  of  waste  matters  from  cities  overtax  Nature's 
arrange/nents  for  their  immediate  destruction,  and  rain-, 
surface-,  aiH  ground-waters  are  all  contaminated  by  animal 
and  manufacturing  wastes.  It  is  probable  that  in  very  few 
cases  is  water  from  air,  stream,  or  well  so  impure  as  to  be 
injurious  when  applied  to  the  skin,  but  only  when  taken  into 
the  stomach.  It  may,  however,  contain  so  much  matter  in 
solution  and  suspension  as  to  unfit  it  for  many  manufacturing 
purposes,  such  as  paper-making  and  the  textile  industries; 
and  for  use  in  these  and  in  washing  kitchen  utensils,  as  well 
as  to  render  it  potable,  it  must  be  uncontaminated  by  objec- 
tionable matters  or  must  be  purified  of  them.  For  other 
purposes,  such  as  extinguishing  fires,  sprinkling  streets, 
flushing  sewers,  etc.,  almost  any  water  is  adapted  which  does 
not  contain  large  amounts  of  suspended  matter. 

Until  within  a  very  few  years  the  principal  aim  of  most 
American  communities  has  been  to  obtain  quantity  of  water, 
with  little   regard  to   its  quality;   and  they  have  so  well  sue- 


^  YNOPSIS.  3 

ceeded  that  we  are  supplying  on  an  average  five  or  six  times 
as  much  water  to  each  citizen  as  do  European  cities.  How- 
ever, compilation  of  mortuary  statistics  by  Health  Boards  of 
different  states  and  cities,  and  comparisons  of  these  with  each 
other  and  with  those  of  foreign  cities,  together  with  a  more 
definite  and  wide-spread  information  on  the  causation  of 
disease,  has  led  to  a  realization  of  the  importance  of  pure 
water,  food,  and  air. 

Largely  for  the  purpose  of  emphasizing  the  importance 
of  this  phase  of  the  subject  the  quality  of  water-supplies  has 
been  the  subject  first  treated  of.  While  this  is  more  a 
chemical  and  bacteriological  than  a  strictly  engineering 
subject,  no  engineer  should  attempt  to  select  a  supply  with- 
out calling  these  branches  of  science  to  his  aid,  and  should 
be  able  to  understand  and  weigh  the  information  thus 
obtained.  In  fact,  many  of  the  problems  not  only  of  design 
but  of  maintenance  also  will  require  for  their  proper  solution 
more  or  less  intimate  knowledge  of  chemistry  and  biology. 

Art.  3.   Elements  of  a  System. 

Before  considering  in  detail  the  design  of  a  system  it  will 
be  well  to  understand  what  elements  go  to  make  up  the 
complex  whole.  In  general  the  water  which  falls  is  to  be 
rendered  available  for  whatever  purposes  man  may  desire  it. 
The  enlarging  and  walling  up  of  a  spring  may  be  considered 
as  the  first  reservoir  construction.  The  roof  from  which  the 
water-butt  receives  its  supply  is  an  elementary  catchment 
area.  The  engineering  features  of  these  and  of  dug  wells  for 
private  supply  are  extremely  simple;  but  public  supplies 
become  more  and  more  complex  as  the  number  of  persons 
and  purposes  to  be  served  increase;  and  the  supply  of  a 
modern  city  with  the  best  water  in  the  best  way  calls  for  a 
high  character  of  engineering  skill. 

A  supply  being  found  which  is  satisfactory  in  quality  and 


4  IVA  TER-SUPPL  V  ENGINEERING. 

quantity — or  the  nearest  to  this  obtainable — it  must  be 
suppb'ed  to  each  consumer  continuously  (although  European 
cities  did  for  years  supply  water  but  a  few  hours  daily),  at  a 
rite  always  sufificient  for  his  hourly  needs,  and  of  the  neces- 
sary purity.  This  may  call  for  storage  to  tide  over  seasons 
of  the  year  when  the  natural  supply  is  deficient;  or  for  puri- 
fication to  improve  the  quality.  If  the  source  is  not  higher 
than  all  points  where  it  is  to  be  used,  the  water  must  be 
raised  to  these.  It  must  be  conducted  from  its  source  to 
each  consumer,  and  the  conduits  provided  with  the  proper 
contrivances  for  supplying  all  public  needs,  such  as  fire- 
service,  street-sprinkling,  and  the  like.  Since  water  is  an 
absolute  daily  necessity,  and  in  a  crowded  city  the  public 
supply  is  generally  the  only  one  available,  there  must  be  no 
possibility  of  an  interruption  of  the  supply  from  any  cause 
whatsoever.  The  quality  also  must  be  preserved,  and  the 
water  as  delivered  be  both  wholesome  and  unobjectionable  to 
any  of  the  senses.  In  some  instances  where  such  water 
cannot  be  obtained  in  sufificient  quantity  for  all  purposes,  a 
secondary  supply  of  less  pure  water  is  used  for  extinguishing 
fires,  street-sprinkling,  and  sewer-flushing. 

Such  a  system  having  been  provided,  it  must  be  so  used 
and  maintained  as  to  deteriorate  as  little  as  possible  both 
in  the  quality  and  quantity  of  water  furnished  and  in  the 
efficiency  of  the  plant;  and,  whether  a  private  or  public 
enterprise,  should  be  conducted  on  sound  business  principles. 

The  subject  of  water-supply  can  best  be  treated  under 
the  general  heads  of  Designing,  Construction,  and  Mainte- 
nance. Each  of  these  considers  the  water  to  be  supplied,  its 
quality  and  quantity ;  the  means  for  obtaining  it  or  making 
it  always  available — wells,  dams,  reservoirs,  pumps,  etc., 
valve-gates,  fire-hydrants,  and  other  contrivances;  and  of 
Maintenance,  the  conduct  of  the  works  from  a  business  point 
of  view  is  an  important  branch. 


CHAPTER    II. 
REQUISITES   OF   A   SUPPLY.     QUALITY. 

Art.  4.     Value  of  Water  Analyses. 

Since  the  quality  of  a  water-supply  is  of  the  greatest  im- 
portance to  all  consumers,  any  water  proposed  for  use  should 
be  most  thoroughly  investigated  before  being  finally  adopted 
for  a  supply.  And  the  engineer,  as  he  generally  must  decide 
concerning  any  given  supply,  should  be  capable  of  doing  so 
intelligently. 

While  it  is  not  necessary  and  is  seldom  possible  that  a 
water-works  engineer  should  be  a  chemist  or  bacteriologist, 
he  should  understand  the  principles  and  aims  of  analyses  and 
be  able  to  interpret  these  when  made  by  experts.  And  first 
he  should  realize  that,  in  the  present  state  of  these  sciences, 
neither  chemistry  nor  biology  can,  alone  or  together,  decide 
finally  as  to  whether  a  water  is  or  is  not  injurious  if  used  as 
a  beverage.  On  the  other  hand,  in  very  few  cases  should 
such  a  decision  be  made  without  their  aid;  and  they  alone  are 
generally  sufificient  to  determine  the  fitness  of  a  supply  for 
use  in  any  given  manufacturing  process,  or  for  irrigation. 

The  characteristics  to  be  considered  are:  impurities 
(injurious  or  otherwise),  appearance,  taste,  color,  and  odor. 

The  impurities  existing  in  water  are  either  organic  or 
mineral,  in  either  solution  or  suspension;  the  organic  may  be 
living  or  dead  organic  matter,  and  may  be  animal  or  vege- 
table.     Mineral   matter  can    generally   be  determined    quite 

5 


6  WATER-SUPPLY  ENGINEERING. 

accurately  as  to  both  kind  and  quantity.  The  organic  can 
be  quite  accurately  determined  as  to  quantity  either  in  solu- 
tion or  suspension;  the  living  organisms  can  be  classified  by 
the  microscopist  with  considerable  minuteness  and  certainty, 
although  much  yet  remains  to  be  learned  in  this  line;  but  of 
dead  and  putrescible  organic  matter,  and  the  products  of 
decomposition  of  this,  little  can  be  learned  through  the 
microscope,  and  chemistry  can  but  discover  the  elements  or 
mineral  compounds  which  enter  into  the  composition  of  such 
matter.  Thus  the  chemist  can  determine  the  amount  of 
nitrogen  in  a  given  water,  and,  knowing  that  sewage  contains 
a  large  amount  of  nitrogen,  may  suspect  sewage  contamina- 
tion. But  he  cannot  say  that  this  mineral  was  not  washed 
out  of  the  air  by  rain,  or  from  peat  deposits  in  the  earth  by 
ground-water. 

In  almost  no  case  is  the  actual  matter  discovered  by  tne 
chemist  injurious  in  quantity.  In  the  average  sewage  the 
total  impurity  is  less  than  one  one-thousandth  the  amount  of 
the  pure  water  which  carries  it;  and  a  river-water  which  the 
senses  would  not  condemn  would  generally  contain  not  more 
than  ^o^^iny  of  impurities.  It  takes  about  looo  drops  of 
water  to  make  one  glassful  {h,  pint),  so  that  the  amount  of 
impurity,  harmless  and  otherwise,  in  a  glass  of  such  water 
would  be  but  ^  the  size  of  a  drop.  It  is  not  therefore  the 
matter  found,  but  the  inference  from  its  presence,  which  is 
important. 

Similarly  the  bacteriologist  may  determine  that  a  cubic 
centimeter  of  water  contains  a  certain  number  of  bacteria, 
but  in  few  if  any  cases  have  pathogenic  bacteria  been  recog- 
nized with  certainty  in  drinking-water;  and  the  number  of 
all  kinds  present  is  but  an  indication  of  the  amount  of  organic 
impurity,  which  may  all  be  harmless.  "  A  water  analysis 
...  is  really  not  an  analysis  at  all,  properly  so  called,  but  is 
a  series  of  experiments  undertaken  with  a  view  to  assist  .the 


REQUISITES    OF  A    SUPPLY.     QUALITY.  / 

judgment  in  determining  the  potability  of  the  supply.  The 
methods  of  conducting  these  experiments  are  largely  influ- 
enced by  the  individual  preference  of  the  analyst,  and  are  far 
from  being  uniform  or  always  capable  of  comparison,  thus 
often  introducing  elements  of  confusion  where  two  or  more 
chemists  are  employed  to  analyze  the  same  water.  Some  of 
the  substances  reported — '  albuminoid  ammonia,'  for  instance 
— do  not  exist  ready  formed  in  the  water  at  all,  and  are  but 
the  imperfect  experimental  measures  of  the  objectionable 
organic  constituents,  which  our  present  lack  of  knowledge 
prevents  our  estimating  directly. 

"  Thus  the  numerical  results  of  a  water-analysis  are  not 
only  unintelligible  to  the  general  public,  but  are  not  always 
capable  of  interpretation  by  a  chemist,  unless  he  be  ac- 
quainted with  the  surroundings  of  the  spot  whence  the 
sample  was  drawn,  and  be  posted  as  to  the  analytical  methods 
employed."     (Mason's  "  Water-supply.") 

Because  the  chemist  cannot  certainly  find  specific  in- 
jurious matter,  except  by  inference,  however,  is  no  reason 
for  neglecting  or  rejecting  his  services;  but  these  should  be 
used  for  all  that  they  are  worth — and  this  may  be  consider- 
able— and  interpreted  in  comparison  with  all  other  available 
data. 

Art.  5.     Interpretation  of  Analyses. 
"  Substances  found  in  water  may  be  classified  as  follows: 

I  Inorganic  or  Mineral 

**  I.   Suspended  Matter  -s  ^         .     c  Animal 
^  i  Organic  ) 

\  Vegetable 


Gaseous 

norganic 

Animal 
Vegetab 
(Nichols'  "Water-supply,  Chemical  and  Sanitary.") 


"2.   Dissolved  Matter    ^  I  Inorganic 

(  SoHd  \  ( 

Organic  \ 
^  (Vegetable." 


8  WATER-SUPPLY  ENGINEERING. 

Much  of  the  suspended  matter  may  become  dissolved  if 
time  be  allowed;  organic  may  be  resolved  into  its  inorganic 
elements;  and  these  may  alter  their  combinations. 

Inorganic  matter  is  seldom  present  in  such  quantities  as 
to  render  injurious  a  water  otherwise  suitable  for  drinking; 
excepting  the  salt  found  in  the  ocean  and  in  certain  under- 
ground waters.  Lime,  salt,  and  iron  are  the  three  mineral 
substances  most  commonly  found.  Whatever  the  mineral,  it 
is  generally  stated  in  the  analysis  directly  in  the  number  of 
parts  found  per  70,000  (grains  per  imperial  gallon);  per 
58,372  (grains  per  U.  S.  gallon);  per  10,000,  100,000,  or 
1,000,000  parts  by  weight;  the  last  being  equivalent  to 
milligrams  per  liter  when  this  amount  of  the  water  in  question 
weighs  1000  grams.  "  Parts  per  100,000"  is  most  generally 
used  in  this  country  for  both  organic  and  inorganic  matter, 
and  will  be  the  unit  adopted  in  this  work  except  where 
otherwise  stated. 

Organic  matter  in  water  appears  as  living  organisms, 
animal  or  vegetable;  products  of  organic  life,  as  albumen, 
urea,  tissue,  etc.,  dissolved  or  suspended;  and  products  of 
decomposition  of  organic  matter,  including  mineral  matters, 
as  salts  of  ammonia  and  carbonic  and  nitric  acids.  Carbon 
and  nitrogen  oscillate  between  the  organic  and  the  inorganic 
state.  Organic  matter  cannot  be  determined  directly  by 
chemical  analyses,  but  only  by  indirect  methods;  the  nitrogen 
compounds  being  generally  taken  as  an  index  of  the  amount 
present,  since  "it  is  the  nitrogenous  organic  matter  which 
has  the  greatest  sanitary  importance,  owing  not  only  to  the 
facility  with  which  it  undergoes  decomposition,  but  also  to 
the  fact  that  nitrogen  is  an  essential  element  in  all  living 
matter.  Analytical  processes  of  great  accuracy  enable  us  to 
determine  nitrogen  in  four  forms;  namely,  as  organic  nitro- 
gen ('  albuminoid  ammonia  '),  as  ammonia,  as  nitrous  acid, 
and     as    nitric    acid."       (Mass.    State     Board    of     Health.) 


REQUISITES    OF  A    SUPPLY.     QUALITY.  9 

Organic  matter  consists  chiefly  of  carbon,  hydrogen,  nitrogen, 
and  oxygen.  When  its  life  departs  it  begins  a  decomposi- 
tion, first  by  oxidation  of  the  carbon,  which  leaves  the 
nitrogen  combined  with  hydrogen  in  the  form  of  ammonia; 
and  subsequently  by  the  oxidation  of  the  ammonia  to  nitric 
acid  (NH3  to  HNO3),  which  generally  combines  with  some 
mineral  base  in  the  water.  The  ammonia  (free  ammonia) 
discovered  by  chemical  analysis  indicates  that  organic  matter 
once  present  has  begun  rapid  decomposition.  That  not  yet 
decomposed,  whether  living  or  dead,  is  changed  by  the 
addition  of  chemicals  to  ammonia  and  given  as  "albuminoid 
ammonia";  while  ammonia  which  has  been  oxidized  is 
recorded  as  "  nitrites  "  or  "  nitrates,"  according  as  nitrous 
or  nitric  acid  has  been  formed.  Albuminoid  ammonia  is 
about  \^  nitrogen,  and  the  amount  of  this  obtained  by  the 
analysis  is  about  one  half  the  organic  nitrogen  present. 
About  15^  of  animal  matter  and  a  much  smaller  part  of  vege- 
table matter  are  nitrogen;  algae  containing  about  j^  nitrogen. 
Hence  the  albuminoid  ammonia,  if  derived  wholly  from 
algae,  times  |f  X  2  X  15  would  give  approximately  the 
amount  of  algae  present. 

The  absorption  of  oxygen  in  the  formation  of  nitrous  and 
nitric  acid  generally  uses  up  much  of  the  free  oxygen  in  the 
water,  and  hence  the  absence  of  oxygen  in  the  water  is  some- 
times considered  as  an  index  of  the  organic  matter  present. 
The  amount  of  oxygen  absorbed  from  a  permanganate  or 
other  oxidizing  agent  by  the  water  to  replace  that  used  up  is 
generally  stated  as  "oxygen  absorbed." 

When  saturated  with  oxygen,  water  at  32°  Fahr.  contains 
1.47  parts  of  this  by  weight  per  100,000;  and  at  80°,  0.81 
parts. 

One  other  determination  is  generally  made  in  investigate 
ing  organic  pollution — the  chlorine;  which,  since  it  is  found 
in  all  urine,  is  taken  as  an  indication  of  sewage  pollution,  if 


lO  WATER-SUPPLY  ENGINEERING. 

existing  in  quantities  greater  than  normal.  Chlorine  cannot 
be  removed  from  water  by  any  method  of  filtration  or  oxida- 
tion, and  hence  any  increase  in  the  amount  present  in  a 
given  water  is  an  indication  that  such  water  has  received  the 
addition  of  a  less  or  greater  amount  of  chlorine,  or  has  been 
reduced  in  amount  by  evaporation. 

High  ammonia,  nitrites,  and  chlorine  together  form  an 
almost  sure  indication  of  sewage  pollution.  The  excreta 
from  each  person  have  been  found  to  contribute  daily  to 
sewage  an  average  of  .015  lbs.  of  free  ammonia,  .003  lbs-  of 
albuminoid  ammonia,  .218  lbs.  of  dissolved  solids,  and  .O42 
lbs.  of  chlorine.  These  amounts  will  of  course  vary  some- 
what with  the  age,  sex,  and  food-matter  of  each  contributor; 
but  by  their  use  an  approximate  idea  can  be  formed  of  the 
pollution  of  a  stream  of  given  flow  which  is  caused  by  a  given 
number  of  sewage  contributors. 

By  the  microscope  living  organic  matter  is  investigated, 
and  in  certain  cases  the  dead  also.  But  for  studying  dis- 
solved or  disintegrated  tissue  or  other  organic  matter  the 
microscope  is  not  adapted.  There  are  very  few  animal  or 
vegetable  organisms  occurring  in  water  which  are  injurious 
to  human  beings,  except  when  taken  in  such  numbers  as  to 
render  the  water  repulsive.  They  may,  however,  give  rise 
to  unpleasant  tastes  in  the  water,  and  for  this  reason  their 
presence  in  considerable  numbers  should  not  be  overlooked. 
There  is  a  class  of  organic  matter,  however,  called  bacteria, 
certain  of  which  are  thought  to  be  the  causes  of  several  dis- 
eases, the  most  important  being  typhoid  fever  and  cholera; 
although  malaria  and  some  other  common  diseases  are  by 
many  attributed  to  water-borne  bacteria.  A  bacterium  is 
about  T^oWfTTT  ^^  Tiriiro"  *^^  ^'^  '"^^  ^"  diameter,  and  one  cubic 
centimeter  may  contain  many  thousands.  Since  but  one 
drop  of  water  can  be  examined  at  a  time,  the  absence  from 
any  given   drop  of  dangerous  bacteria  is  no  indication   that 


REQUISITES    OF  A    SUPPLY.      QUALITY.  II 

some  other  of  the  million-and-a-half  drops  supplied  daily 
on  an  average  to  each  consumer  may  not  contain  such.  More- 
over, in  the  present  state  of  bacteriology  we  cannot  certainly 
identify  the  particular  bacterium  of  typhoid  or  of  cholera, 
and  about  the  only  determination  which  can  be  made  is  a 
quantitative  one.  Of  100,000  bacteria  in  a  cubic  centimeter 
of  water,  not  one  may  be  morbific;  but  the  presence  of  this 
number  indicates  organic  matter  which  may  furnish  food  for, 
or  be  otherwise  indicative  of,  the  presence  of  such  bacteria; 
and  hence  water  high  in  bacteria  is  generally  looked  upon 
with  suspicion,  particularly  if  known  to  receive  sewage,  which 
may  contain  the  dejecta  of  typhoid  and  cholera  patients. 

Art.  0.     Inorganic  Matter. 

Iron,  lime,  magnesia,  chlorine  (usually  as  chloride  of 
sodium  or  common  salt),  sulphuric  acid  (generally  as  sulphate 
of  lime,  magnesia,  sodium,  or  potassium),  carbonic  acid  (both 
free  and  as  carbonate  of  lime  or  of  magnesia),  are  the  mineral 
matters  most  commonly  found  in  solution  in  natural  waters. 
In  suspension  may  be  found  clay,  fine  sand,  and  other  soil 
constituents,  varying  in  size  from  ^  ^  q^q  q  ^  of  an  inch  to  large 
sand  or  gravel. 

Iron  is  not  unhealthful  when  occurring  in  drinking-water 
in  relatively  large  amounts;  but  since  one  part  to  200,000  of 
water  is  appreciable  to  the  taste,  more  than  this  should  not 
be  permitted  in  a  public  supply;  more  especially  since  less 
than  this  amount  in  washing  water  will  discolor  clothes,  and 
will  cause  a  brown  sediment  when  left  standing  in  the  open 
air.  Iron  is  derived  from  iron  deposits  in  the  soil  and  deeper 
strata,  dissolved  out  by  surface-  and  ground-waters,  and  from 
peaty  and  other  vegetable  matter.  Most  vegetable  matter 
contains  more  or  less  iron, — leaves  from  .01^  to  .06^,  grass 
about  .006^,  and  black  peaty  muck  o.c^io  (Boston  Water 
Board  experiments),  and  much  of  this  is  dissolvable  by  water, 


12  WATER-SUPPLY  ENGINEERING. 

and  probably  is  largely  responsible  for  the  color  in  swamp 
and  peaty  waters.  Such  discolored  peaty  waters  are  often 
wholesome,  and  some  of  the  purest  water-supplies  in  southern 
New  Jersey  are  highly  colored.  Peaty  waters  are  not  always 
harmless,  however,  but  have  been  known  to  cause  enteric 
diseases,  probably  because  of  too  large  quantities  of  organic 
matter. 

Lime  and  magnesia  occur  in  water  as  carbonates  or  sul- 
phates, or  other  soluble  salts.  The  carbonates  cause  a 
"  temporary  hardness,"  the  other  salts  "  permanent  hard- 
ness." Carbonates  are  caused  by  the  carbonic  acid  contained 
in  a  water  dissolving  lime  or  magnesium  from  the  rock  it 
passes  over  or  through.  When  water  is  boiled,  carbonic 
acid  is  expelled  and  the  lime  or  magnesium  is  left  in  suspen- 
sion, and  forms  a  deposit,  in  boilers  a  "scale,"  the  water 
being  thus  rendered  "soft."  In  permanently  hard  water 
the  salts  are  dissolved  by  the  water  itself  and  do  not  separate 
out  by  boiling.  The  same  water  may  be  both  temporarily 
and  permanently  hard.  Such  hardness  as  is  ordinarily  found 
in  water  is  not  unhealthy,  although  slight  intestinal  trouble 
may  be  caused  by  the  change  from  soft  water  to  hard,  but 
also  from  hard  to  soft.  It  is  not  probable  that  hard  water 
causes  deposits  of  calcareous  matter  in  the  bladder.  The 
serious  objection  to  hard  water  is  the  formation  of  scale  in 
boilers  and  the  waste  of  soap  resulting  from  its  use.  In 
general  it  may  be  said  that  each  grain  of  carbonate  of  lime 
per  gallon  of  water  compels  the  use  of  two  additional  ounces 
of  soap  per  lOO  gallons  of  water.  The  expense  to  boiler- 
users  is  even  greater.  The  sulphate  scale,  which  is  deposited 
at  about  260°  Fahr. ,  is  much  more  injurious  than  the  car- 
bonate, because  it  forms  a  denser  and  harder  incrustation. 
The  expense  of  cleaning  and  repairing  boilers,  due  to  this 
scale,  for  a  mileage  of  362,756  on  the  Nebraska  Division  of 
the  U.  P.  R.  R.  in   1897-8  was  $2860,  or  8  cents  per  mile, 


REQUISITES   OF  A    SUPPLY.      QUALITY.  1 3 

in  addition  to  which  the  total  mileage  of  each  engine  was 
reduced  probably  one  half.* 

Sulphates  of  sodium  and  potassium  occur  in  small  quan- 
tities in  some  waters  and  cause  foaming  in  boilers,  but  no 
deposits.  Sulphate  of  magnesium  forms  a  boiler-scale,  and 
the  sulphuric  acid  is  set  free  as  a  corrosive  element.  Chlorine 
generally  occurs  in  water  in  the  form  of  common  salt  (NaCl). 
Besides  the  urine  of  man  and  other  animals,  the  sources  of 
most  chlorine  in  water  are  the  ocean,  from  which  it  is  carried 
by  evaporation  and  held  in  solution  by  the  rain ;  and  salt 
deposits  on  the  surface,  as  on  the  western  desert,  or  in  the 
ground,  as  in  western  New  York,  Ohio,  and  Kentucky. 
Rain-water  in  certain  parts  of  Massachusetts  contains  2.5 
parts  of  chlorine  per  100,000;  and  7  parts  have  been  found 
in  rain-water  in  England.  A  well  in  St.  Augustine,  Fla., 
contains  196  parts  per  100,000  of  salt,  and  those  in  Onondaga 
County,  N.  Y.,  contain  about  15,000  parts  per  100,000; 
while  the  Great  Salt  Lake  contains  20,000  parts.  The 
waters  last  mentioned  are  not  potable,  and  cannot  be  used 
for  boilers,  or  probably  for  any  purpose  for  which  water  is 
required.  But  the  amount  contained  in  any  rain-water  or 
surface-water  deriving  all  its  salt  from  the  atmosphere  is 
neither  injurious  nor  unpalatable,  nor  harmful  to  boilers; 
although  it  may  prevent  its  use  for  certain  manufacturing 
purposes. 

If  it  were  not  for  the  fact  that  salt  is  contained  in  sewage, 
it  would  not  generally  be  necessary  to  determine  its  quantity 
in  water.  To  decide  how  much  of  that  found  in  a  given 
water  is  due  to  sewage  pollution  it  is  necessary  to  know  the 
amount  present  in  uncontaminated  ("  normal  ")  water  in  the 
locality  in  question.  This  is  generally  determined  by  analyz- 
ing surface-water  (if  such  be  the  water  whose  analysis  is 
desired)  taken  above  any  possible  sewage  pollution,  and 
comparing  its  chlorine  with  that  of  the  water  in  question. 

*For  test  for  Hardness  see  Appendix  E,  page  555. 


14  WATER-SUPPLY  ENGINEEEING. 

(If  it  be  ground-water  little  can  be  learned  as  to  sewage  pol- 
lution from  the  chlorine  determination.)  Several  State 
Boards  of  Health  have  made  such  analyses  in  all  parts  of 
their  States,  and  thus  determined  the  "  normal  chlorine  "  for 
each  section.  This  is  found  to  vary  quite  closely  with  the 
distance  from  the  ocean.  Plate  I  shows,  by  means  of 
**  isochlors,"  the  normal  chlorine  throughout  Massachusetts 
and  Connecticut,  as  determined  by  their  respective  State 
Boards. 

If  the  water  at  any  place  contains  more  than  the  normal 
chlorine  it  should  be  looked  upon  with  suspicion  until  further 
examination  reveals  the  source  of  the  excess. 

Lead  and  zinc  are  dissolved  from  service-pipes  by  some 
waters,  and  in  relatively  large  quantities  may  cause  serious 
poisoning.  In  Lowell,  Mass.,  water  high  in  carbonic  acid 
has  recently  given  trouble  when  delivered  through  lead  or 
galvanized  pipe.  23  parts  of  lead  per  100,000  were  found 
in  one  sample  which  flowed  through  285  feet  of  lead  service- 
pipe 

Art.  7.     Organic  Matter. 

Living  organic  matter,  or  such  as  has  not  begun  or  does 
not  accompany  putrefaction,  in  the  quantities  ordinarily 
found  in  water  is  not  often  injurious.  These  organisms  vary 
in  size  from  the  smallest  bacterium  to  the  largest  fish. 
There  are  perhaps  a  few  vegetable  organisms  which  are 
poisonous;  many  which,  if  taken  into  the  stomach  in  large 
quantities,  would  produce  nausea  or  more  serious  enteric 
troubles;  but  no  water  which  would  be  used  for  drinking 
purposes  except  under  the  most  extreme  compulsion  contains 
a  sufficient  amount  of  such  matter  to  be  seriously  injurious; 
always  excepting  certain  bacteria.  Many  organisms  both 
animal  and  vegetable  are  beneficial  to  the  water  in  that  they 
purify  it  from  dead  organic  matter.      The  most  numerous  of 


REQUISITES   OF  A    SUPPLY.     QUALITY. 


15 


Plate  I. — Isochlors  of  Massachusetts  and  Connecticut. 
(From  Reports  of  the  State  Boards  of  Health.) 


1 6  WATER-SUPPLY  ENGINEERING. 

the  smaller  vegetable  organisms  found  are  alga;,  fungi>  and 
bacteria — the  two  former  being  generally  visible  to  the  naked 
eye.  Of  animals  other  than  fishes  the  protozoa,  spongiana^ 
rotifera,  entomostraca,  and  certain  mollusks  are  those  most 
often  found.  Of  these  the  animals  live  on  vegetable  matter 
and  other  animals,  the  vegetable  organisms  upon  "  mineral- 
ized "  organic  matter  (bacteria,  however,  seem  to  possess 
the  animal  characteristic  of  feeding  upon  organic  matter). 
Both  thus  assist  in  purifying  the  water,  not  only  of  organic 
impurities,  but  of  mineral  ones  also.  Many  ground-waters 
furnish  the  requisite  food,  generally  in  the  form  of  nitrogen, 
for  immense  numbers  of  algae,  of  which  over  2000  species  are 
known. 

These  organisms,  whether  living  or  dead,  seldom  give 
any  injurious  properties  to  water;  but  many  species  of  algae, 
including  some  of  the  green  ones,  give  off  when  dead  an  odor 
described  as  "  fishy,"  "  cucumber,"  etc.,  which  is  not 
injurious,  but  is  very  unpleasant* 

The  way  in  which  certain  bacteria  produce  disease  is  not 
understood;  nor  is  it  known  whether  a  single  bacterium  may 
suffice  for  this  purpose,  although  it  is  certain  that  consider- 
able numbers  of  pathogenic  ones  may,  under  some  circum- 
stances, be  taken  into  the  stomach  without  apparent  effect. 
We  do  know  that  in  many  instances  the  contamination  of  a 
water-supply  with  the  excreta  of  typhoid-fever  patients  has 
been  followed  by  a  great  number  of  cases  of  such  fever 
among  its  consumers;  and  that  the  only  apparent  difference 
always  found  between  the  excreta  of  a  typhoid  patient  and 
that  of  any  others  is  the  presence  of  a  certain  bacterium,  the 
bacillus  typhosus,  in  such  excreta.  The  connection  between 
cholera  and  the  spirillum  cholerae  Asiaticae  seems  to  be 
similarly  intimate.  The  former,  however,  is  the  only  disease 
common  in  this  country  whose  bacterial  source  seems  proven. 

About    loio  of  typhoid  cases  are  fatal.     The  majority  of 

*  See  Appendix  E,  page  556. 


REQUISITES    OF  A    SUPPLY.      QUALITY. 


17 


cases  are  persons  between  18  and  35  years  of  age.  It  takes 
from  9  to  25  days  for  the  disease  to  make  itself  apparent — 
14  or  15  days  is  the  most  common  period — and  the  average 
length  of  sickness  is  40  to  50  days.  Typhoid  fever  occurs 
most  frequently  in  the  autumn ;  as  illustrated  by  the  follow- 
ing table: 

DEATHS    FROM    TYPHOID   AND  TYPHO-MALARIAL  FEVERS;  BY  MONTHS. 


Connecticut:  average  for 
eight  years.  (State  Bd. 
of  Health.) 

Ohio;  1892.  (State  Board 
of  Health.) 


c 

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24.9 
40 


Although  a  temperature  somewhat  under  150°,  if  con- 
tinued for  a  few  minutes,  is  fatal  to  typhoid  bacteria,  they 
have  been  known  to  live  for  days  and  weeks  in  both  pure 
and  impure  water  and  in  ice.  It  thus  appears  that,  once 
introduced  into  a  river,  the  danger  exists  of  their  being  in 
any  given  glass  of  water  taken  therefrom;  although  this 
danger  is  reduced  by  reducing  the  average  number  of  such 
bacteria  to  each  gallon  of  the  water.  A  given  river-water 
may  contain  millions  of  bacteria  per  cubic  centimeter,  of 
which  but  a  few  are  pathogenic;  and  these  few  cannot  often 
be  recognized  with  certainty;  but  it  is  considered  probable, 
from  known  data,  that  the  smaller  the  total  number  of 
bacteria  the  smaller  the  number  of  pathogenic  ones.  It  is 
impossible  to  set  a  limit  to  the  number  of  bacteria  permissi- 
ble in  drinking-water,  but  this  should  be  the  lowest  possible. 
One  hundred  per  cubic  centimeter  is  the  provisional  limit  set 
for  filtered  water  by  the  German  Imperial  Board  of  Health 
in  1892. 

Lifeless  organic  matter  in  the  presence  of  moisture  very 
quickly  begins  to  decompose,  and  if  oxygen  be  present  in 
sufficient  quantities  "  mineralizes  "  into  nitrates,  this  process 


1 8  WATER-SUPPLY  ENGINEERING. 

being  assisted  by  bacteria.  These  nitrates  are  of  themselves 
harmless,  but  unoxidized  putrescible  or  putrescent  matter,  or 
the  bacteria  of  putrefaction,  are  thought  to  produce  enteric 
diseases  which  may  be  of  a  serious  nature  if  such  matter 
exists  in  relatively  large  quantities.  18.7  parts  of  solids,  of 
which  9.2  were  organic,  in  the  water-supply  of  Long  Branch, 
N.  J.,  in  1887  caused  a  severe  epidemic  of  diarrhoea. 

It  is  neither  possible  nor  desirable  to  place  a  limit  to  the 
amount  of  organic  matter  permissible  in  a  drinking-water, 
since  it  is  more  the  quality  than  the  quantity  of  such  matter 
which  is  important.  Such  matter,  when  from  leaves  and 
other  vegetable  bodies,  may  be  perfectly  harmless  while 
fresh;  a  little  later,  while  decomposing,  it  may  be  injurious; 
and  later  still,  when  oxidized,  it  may  again  be  harmless.  If 
the  albuminoid  ammonia  in  a  river  below  a  town  be  much 
greater  than  in  the  same  river  above  possible  sewage  con- 
tamination, such  water  should  be  avoided  for  its  organic 
matter;  and  if  either  this,  free  ammonia,  or  nitrogen  be 
present  in  large  quantities,  it  should  be  avoided  for  the 
bacteria  probably  accompanying  these. 

Organic  matter  seldom  renders  water  objectionable  from 
other  than  a  sanitary  point  of  view,  except  in  the  physical 
condition  and  character  of  suspended  matter. 

Art.  8.     Physical  Properties. 

The  matter  in  suspension  in  a  water  may  be  so  consider- 
able as  to  interfere  with  its  use  for  manufacturing  purposes 
or  boiler  supply,  and  render  it  unattractive  in  appearance. 
When  such  matter  consists  of  clay,  sand,  etc.,  it  may  in 
many  cases  be  drunk  with  impunity,  especially  when  the 
stomach  becomes  habituated  to  it.  For  household  purposes, 
however,  a  turbid  water  is  undesirable;  although  many 
American  cities  use  water  which  at  times  appears  tawny 
yellow  or  dark  gray  in  a  drinking-glass,  and  contains    1800 


REQUISITES    OF  A    SUPPLY.      QUALITY.  1 9 

parts  of  matter  in  suspension  per  100,000  for  a  short  time 
during  floods. 

While  the  clay  and  sand  washed  into  a  river  are  not 
themselves  particularly  injurious  to  health,  they  serve  to  call 
attention  to  the  fact  that  more  objectionable  impurities  may 
have  been  washed  from  the  ground-surface  at  the  same  time, 
such  as  human  excreta,  manure,  fertilizers,  etc.  The  amount 
of  turbidity  is  usually  expressed  as  the  reciprocal  of  the 
greatest  distances  from  the  surface  of  the  water,  expressed  in 
inches,  at  which  a  platinum  wire  .04  in.  thick  can  be  seen. 
Thus,  if  such  wire  just  disappears  at  5  inches  the  turbidity 
is  0.2* 

The  color  of  a  water  tells  little  of  its  characteristics,  since 
an  unobjectionable  one  may  have  considerable  color,  while 
another  seriously  polluted  may  be  clear  and  sparkling.  But 
color  is  apt  to  prejudice  consumers  against  a  supply,  and  this 
should  be  taken  into  consideration.  Many  waters  have  a 
higher  color  at  one  time  than  at  another,  without  any  change 
in  the  quantity  of  impurities  present.  Thus  ferrous  oxide  in 
solution  may,  by  absorbing  oxygen,  become  insoluble  ferric 
oxide  causing  a  dark  color,  which  again  disappears  when  this 
settles  out  or  yields  part  of  the  oxygen  to  organic  matter  in 
the  water.  Color  is  determined  by  comparison  with  a  fixed 
arbitrary  standard  or  set  of  standards,  the  depth  of  either 
water  or  standard  being  varied  to  cause  the  color  of  the  two 
to  agree.  A  Nessler  scale  of  17  standards,  recommended  by 
Prof.  A.  R.  Leeds,  and  the  platinum  standard  of  Allen 
Hazen,  are  the  most  commonly  used.  These  standards 
correspond  at  0.40;  but  1.50  by  the  platinum  scale  equals 
2.00  by  the  Nessler.  The  greater  the  number  the  darker 
the  color. 

No  standard  for  odor  and  taste  have  been  or  can  well  be 
set.  These,  like  color,  may  or  may  not  be  relative  to  the 
impurity    of    the    water,    but    may    easily   influence    popular 

*  See  Appendix  E,  page  555. 


20  WA  TER-SUPPL  V  ENGINEERING. 

opinion,  and  even  produce  nausea  in  sensitive  constitutions. 
A  considerable  odor  is,  however,  generally  indicative  of 
undesirable  pollution. 

A  cool  water  is  pleasanter  as  a  beverage  than  a  warm, 
and  is  less  liable  to  foster  the  growth  of  vegetable  organisms. 
But  this  is  a  question  more  of  the  construction  of  the  reser- 
voirs, piping,  etc.,  than  of  the  supply  at  its  source. 

Art.  9.     Statistics  of  Disease  in  Relation  to 
Drinking-water. 

The  bacillus  typhosis  cannot  be  followed  in  its  course 
from  the  dejecta  of  a  typhoid  patient  along  a  watercourse  or 
in  surface-water  to  the  intestines  of  its  victim;  but  its 
responsibility  for  the  infection  is  proved  by  indirect  evidence 
only.  The  relation  most  important  to  the  engineer  is  that 
appearing  to  exist  between  sewage-polluted  water  and  typhoid 
fever.  There  are  other  mediums  of  typhoid  infection  besides 
drinking-water;  but  the  fact  that  purification  of  the  water- 
supply  in  almost,  if  not  quite,  every  case  greatly  reduces  the 
typhoid  rate  seems  to  argue  that  drinking-water  is  by  far  the 
most  important  one.  The  two  well-known  instances  of 
Hamburg  and  Altona  in  Germany,  and  Lawrence  in  this 
country,  are  but  pronounced  illustrations  among  a  great 
number  of  cases  of  the  effect  of  water  on  typhoid  death-rates. 
Of  Altona  and  Hamburg — two  cities  really  one  but  for  their 
distinct  government  and  public  works,  using  the  same  river 
for  a  water-supply,  that  of  Altona,  however,  being  polluted 
with  Hamburg's  sewage,  but  filtered  carefully  before  use — 
Hamburg  in  1892  lost  8605  by  cholera,  a  rate  of  1344  per 
100,000  inhabitants,  while  Altona  lost  but  328,  a  rate  of  230. 
Prof.  Koch  says:  "  Cholera  in  Hamburg  went  right  up  to  the 
boundary  of  Altona  and  stopped.  In  one  street,  which  for 
a  long  way   forms  the  boundary,  there  was  cholera  on   the 


iSgo 

1891 

1892 

1893 

1S94 

1895 

1S96 

1897 

123 

115 

95 

69 

48 

31 

18.6 

16.2 

RE  Q  UISI TES    OF  A    S  UP  PL  Y.      QUALITY.  21 

Hamburg  side,  whereas  the  Altona   side  was  free  from  it  "  — 
undoubtedly  because  of  the  different  water-supplies. 

Lawrence,  Mass.,  has  drawn  its  water-supply  from  the 
Merrimac  River  since  1875.  In  September,  1893,  sand- 
filtration  was  begun,  but  the  use  of  unfiltered  water  in  the 
mills  has  been  only  gradually  abandoned  since  then.  The 
typhoid  death-rates  before  and  since  1893  have  been  as 
follows  (per  100,000): 

1893   1S94   1895   1S96   1897   1898 

13-9 

Referring  to  Plate  II,  page  24,  it  is  seen  that  a  consider- 
able reduction  in  the  typhoid  rate  followed  the  introduction 
into  Newark  of  the  Pequannock  water,  derived  from  a 
sparsely  settled  watershed,  the  filthy  Passaic  having  been  the 
former  source  of  supply.  The  introduction  of  a  purer  supply 
and  settling-basins  in  St.  Louis  in  1894  resulted  in  the 
immediate  reduction  of  typhoid  rates;  as  was  also  the  case 
when  Chicago  began  the  use  of  the  four-mile  intake  instead 
of  the  short  one  formerly  used.  The  same  result  appears 
also  in  the  records  of  Lowell  and  Atlanta. 

In  the  winter  of  1890  and  1891  a  typhoid  epidemic 
travelled  progressively  down  the  Mohawk  and  Hudson  rivers, 
appearing  at  Amsterdam  and  Schenectady  (on  the  Mohawk) 
during  the  latter  part  of  1890  and  at  Cohoes,  Green  Island, 
Troy,  Albany,  and  Catskill  in  the  early  part  of  1891.  AH 
of  these  cities  derive  their  water  from  and  empty  their 
sewage  into  the  Hudson,  or  its  tributary,  the  Mohawk. 

"  If  the  drinking-water  supplied  to  cities  is  an  index  of 
their  healthfulness  as  measured  by  the  typhoid-fever  death- 
rates,  we  should  expect  to  find  some  sort  of  relation  existing 
between  the  quality  of  the  water  and  the  typhoid  death-rates. 
Of  course  it  is  unreasonable  to  expect  to  find  such  an  exact 
relation   that  there  would  be  no  variation   from   the  rate   for 


22  IV A  TER-SUPPL  Y  ENGINEERING. 

each  different  classification;  there  must  be  overlapping,  as 
local  conditions  may  make  a  certain  water  more  subject  to 
pollution  than  another.  As  a  general  thing,  we  should 
expect  to  find  that  cities  whose  water  is  kept  perfectly  secure 
from  contamination,  such  as  use  spring-water  secured  in 
mountains  where  no  pollution  is  possible,  would  have  the 
lowest  death-rates,  and  the  range  of  fluctuation  would  be 
very  small,  comparatively  speaking.  Next  we  should  expect 
to  find  that  water  properly  filtered,  as  is  done  extensively  in 
Europe,  would  show  a  low  rate  and  one  without  much 
fluctuation,  provided  the  operation  is  carefully  and  intelli- 
gently carried  on.  Next  in  purity  we  should  expect  to  find 
ground-waters,  and  in  these  there  might  be  accidental  pollu- 
tion that  would  cause  considerable  fluctuation.  Then  follow, 
in  the  order  of  their  liability  to  contamination,  large  im- 
pounding reservoirs,  where  legal  measures  are  taken  to 
restrict  pollution;  large  rivers,  either  normal,  or  where  great 
volume  and  absence  of  any  considerable  evident  place  of 
pollution  within  a  great  distance,  coupled  with  dispersion, 
sedimentation,  and  nitrification,  may  have  brought  a  pre- 
viously polluted  river  back  to  its  normal  condition.  Thea 
follow  great  lakes,  whose  waters  at  great  distances  from 
polluting  sources  are  pure,  but  which  are  liable  to  pollution 
near  the  shores  (in  this  class,  from  the  relative  positions  of 
the  intakes,  we  should  expect  to  find  rates  varying  from 
those  of  a  very  healthful  city  to  those  of  the  most  infected); 
upland  streams  and  small  gathering-grounds  where  no  special 
precautions  may  be  taken  to  restrict  pollution  of  the  water- 
sheds; and,  finally,  rivers  and  sources  known  to  be  polluted 
with  sewage.  In  cities  using  such  supplies  we  should  expect 
to  find  high  typhoid-fever  death-rates,  and  a  considerable 
variation  of  rates  from  year  to  year."  (Fuertes'  "  Water  and 
Public  Health.")  J.  H.  Fuertes  has  collected  and  arranged 
data    from    a    large    number    of    cities,   both  American    and 


REQUISITES   OF  A    SUPPLY.      QUALITY.  23 

European,  and  these  data  are  shown  on  Plate  II,  page  24, 
as  classified  by  him.      His  classification  is  as  follows: 

"  Class  A.  Mountain  springs  with  sources  undoubtedly 
beyond  the  danger  of  pollution. 

"  Class  B.   Water  properly  purified  by  slow  sand-filtration. 

"  Class  C.    Pure  ground-water  supplies. 

"  Class  D.  Surface-water  supplies  with  large  impounding 
reservoirs  and  legal  provisions  against  pollution. 

"  Class  E.  Large  normal  rivers,  or  rivers  in  which  the 
pollution  may  be  considered  to  have  greatly  vanished  through 
the  agency  of  sedimentation,  dilution,  and  other  causes. 

"  Class  F.  Large  inland  lakes,  which  may  be  more  or  less 
subject  to  pollution. 

"  Class  G.  Upland  streams  and  small  lakes  with  limited 
watersheds  which  are  more  or  less  inhabited. 

"  Class  H.  All  rivers  and  public  and  private  wells  which 
are  known  to  be  polluted  with  sewage  and  other  infectious 
matter  to  varying  degrees." 

From  a  study  of  these  data  Fuertes  finds  that  in  cities 
using  filtered  water  94^  of  the  death-rates  per  100,000  are 
more  than  3,  83^  are  less  than  20,  and  yjio  are  between  3 
and  20 ;  that  in  cities  using  groiutd-waters  98^  of  the  death- 
rates  per  100,000  are  more  than  5,  J'jio  are  less  than  32,  and 
'J^<fc  are  between  5  and  32;  that  in  cities  using  inipotinded 
waters  gy^  of  the  death-rates  per  100,000  are  above  15,  80^ 
are  less  than  35,  and  '/'j';^  fall  between  15  and  35;  that  in 
cities  using  the  waters  of  large  Jiornial  rivers  90^  of  the 
death-rates  per  100,000  are  above  17,  85^  are  less  than  38, 
and  75,'^  are  between  17  and  38;  that  in  cities  using  the 
waters  of  th^  great  lakes  <^i<fo  of  the  death-rates  per  100,000 
are  over  18,  80^  are  less  than  54,  and  73^  are  between  18 
and  54;  that  in  cities  using  the  waters  of  upland  streams,  etc., 
92f^  of  the  death-rates  per  100,000  are  over  29,  80;;^  are  less 
than  58,  and  72^  are  between  29  and  58;   that  in  cities  using 


24 


WA  TER-SUPPL  Y  ENGINEERING. 


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Plate  II. — Death-rates  Per  100,000  P 
(See  also  Appendix  A, 


ER  Annum  from  Tyi'Hoid  Fever. 
Table  No.  73.) 


REQUISITES   OF  A    SUPPLY.      QUALITY. 


25 


polluted  waters  95^  of  the  death-rates  per  100,000  are  over 
40,  and  only  65^  fall  between  50  and  100,  the  upper  limit 
frequently  exceeding  300.  ("  Water  and  Public  Health.") 
Stated  in  another  way,  75,^  of  the  death-rates  in  American 
cities  fall  between  the  following  limits  for  each  class  of 
supplies: 


Mountain 
Springs. 

Filtered 
Water. 

Ground- 
Water. 

Impounded 
Waters. 

Large  Nor- 
mal Rivers. 

Great 
Lakes. 

Upland 
Streams. 

Polluted 
Waters. 

2  to  10 

3  to  20 

5  to  32 

15  to  35 

17  to  38 

19  to  53 

28  to  57 

39-1004- 

The  above  are  deaths  only;  but  since  only  9  to  12  per 
cent  of  typhoid  cases  ordinarily  prove  fatal,  the  chance  of  any 
citizen  being  infected  with  this  disease  is,  say,  10  times  these 
rates.  From  a  humanitarian  point  of  view  it  is  the  duty  of 
all  concerned  to  prevent  as  many  deaths  as  possible;  from 
the  utilitarian,  the  value  to  the  community  of  the  lives  lost 
must  be  considered.  Rochard  gives  this  as  the  sum  "that  he 
has  cost  his  family,  the  community,  or  the  state  for  his  living, 
development,  and  education.  It  is  the  loan  which  the  indi- 
vidual has  made  from  the  social  capital  in  order  to  reach  the 
age  when  he  can  restore  it  by  his  labor,"  This  sum  may 
vary  from  S500  to  $50,000,  but  a  conservative  average  would 
probably  be  $5000.  Since  by  far  the  greater  part  of  the 
typhoid  victims  are  in  their  prime,  and  the  majority  are 
among  the  wealthier  class,  this  value  is  above  rather  than 
below  the  average.  Thus,  where  polluted  waters  are  used 
each  citizen,  as  part  of  the  community,  loses  annually  by 
deaths  from  $1.50  to  $15  worth  of  potential  labor,  which 
might  be  reduced  by  filtration  or  the  use  of  mountain  springs 
to  from  10  cents  to  $1.00.  Moreover,  the  average  length  of 
sickness  being,  say,  45  days,  each  citizen  would,  with  polluted 
supply,  lose  annually  from  .135  to  1.35  days  of  his  fellow 
citizen's  labor,   which  at  $2  and  the  doctor's  bills  at  a  like 


26  WATER-SUPPLY  ENGINEERING. 

sum  would  amount  to  from  $0.54  to  $5.40;  making  a  total 
annual  loss  of  from  $2  to  $20  per  capita,  as  against  a  possible 
$0.14  to  $1.36  with  a  pure  water-supply.  At  Plymouth, 
Pa.,  in  1885  (population  8000)  1 104  cases  of  typhoid  fever 
and  1 14  deaths  resulted  from  discharging  the  dejecta  of  one 
patient  into  the  water  of  a  small  impounding  reservoir.  The 
care  of  these  patients  cost  $67,100.17,  and  the  loss  of  wages 
by  those  who  recovered  $30,020.08;  an  actual  money  loss  in 
one  year  of  $12.14  P^^"  capita;  or  $83.39  P^''  capita  if  the 
value  of  each  life  be  placed  at  $5000. 

Art.  10.     Summary:  Requisite  Quality. 

It  appears  to  have  been  demonstrated  that  an  impure 
drinking-water  is  a  very  important  cause  of  diarrhoea,  typhoid 
fever,  cholera,  and  probably  a  number  of  other  diseases; 
typhoid  fever  and  cholera  being  communicated  by  sewage- 
pollution.  It  is  probable  also  that  the  immediate  cause  of 
these  two  diseases  is  found  in  water-borne  parasitic  bacteria ; 
while  that  of  the  other  enteric  diseases  may  be  either  bacteria 
or  matter  which  acts  mechanically  as  an  irritant.  By  its 
morbific  qualities  impure  water  may  be  considered  to  cause 
a  loss  to  the  community  of  from  $2  to  $20  per  capita  per 
annum;  or  $1.86  to  $18.64  more  than  if  pure  water  were 
used;  and  hence  this  sum  capitalized,  or,  say,  $46.50  to  $465 
per  capita,  could,  from  a  utilitarian  point  of  view,  be  profit- 
ably spent  in  purifying  the  water  or  obtaining  it  from  an 
uncontaminated  source.  In  deciding  what  can  be  called  a 
pure  water,  or  what  limit  of  impurity  can  be  fixed  for  potable 
water,  great  difficulty  arises.  Bacteriological  analysis  can 
inform  us  of  the  approximate  number  of  bacteria  per  cubic 
centimeter  in  a  water,  but  not  certainly  as  to  the  presence  of 
pathogenic  ones.  Chemical  analysis  can  inform  us  of  the 
amount  of  organic  matter  which  is  and  which  has  been 
present,  but  not  as  to  whether  this  is  animal  or  vegetable, 


REQUISITES    OF  A    SUPPLY.      QUALITY.  2/ 

r.iorbific  or  otherwise.  Hence  no  absolute  standards  can  be 
based  upon  the  determinations  of  either  or  both  of  these 
alone.  The  probability  of  either  bacteria  or  organic  matter 
being  of  such  a  character  as  to  render  the  water  dangerous 
must  be  judged  from  their  probable  source  and  origin.  A 
great  increase  of  organic  matter  in  a  river  below  a  city  as 
compared  with  the  same  river  above  indicates  sewage-con- 
tamination and  danger;  while  a  like  increase  in  flowing 
through  a  forest  is  probably  due  to  leaves  and  other  vege- 
table matter  only.  It  can  be  said,  however,  that  a  water  low 
in  bacteria  and  in  organic  impurities  is  in  all  probability  a 
safe  one;  that  a  water  with  only  a  moderate  amount  of  these 
present  which  comes  from  an  unpopulated  watershed  or  a 
deep  well  is  likewise  probably  safe;  but  that  a  water  should 
be  treated  with  suspicion  which  is  high  in  bacteria  and 
organic  matter,  or  which,  containing  a  moderate  amount  of 
these,  is  subject  to  sewage  or  any  human  contamination. 

For  other  than  sanitary  reasons  a  water-supply  should 
contain  little  sediment  or  dissolved  mineral  matter  or  acids, 
and  should  have  no  appreciable  color,  taste,  or  odor;  and  the 
cooler  it  can  be  delivered  to  the  consumer  the  better. 

For  water  which  is  to  be  used  for  irrigation  the  require- 
ments as  to  quality  are  seldom  considered,  since  few  waters 
available  for  this  purpose  contain  matters  injurious  to  vege- 
table life.  Large  amounts  of  alkaline  salts,  alum,  and  most 
other  mineral  impurities  are  not  permissible;  but  excepting 
the  first  (chloride,  sulphate,  and  particularly  carbonate  of 
sodium)  and  lime  none  of  these  are  often  found  in  appreci- 
able quantities  in  large  volumes  of  waters,  and  the  lime  is 
beneficial  in  many  instances.  Sediment  is  desirable  for  most 
soils,  as  it  has  considerable  fertilizing  value.  "In  the  valley 
of  Moselle,  France,  on  land  absolutely  barren  and  worthless 
without  fertilization,  the  alluvial  matter  deposited  by  irriga- 
tion from  turbid  water  renders  the  soil  capable  of  producing 


28  WATER-SUPPLY  ENGINEERING. 

two  crops  a  year.  In  the  valley  of  the  Durance,  France,  the 
turbid  waters  of  that  stream  bring  a  price  for  irrigation  which 
is  ten  and  twelve  times  greater  than  that  paid  for  the  clear 
cold  water  of  the  Sorgues  River.  It  has  been  estimated  that 
on  the  line  of  the  Calloway  Canal  in  California  land  which 
has  been  irrigated  with  the  muddy  river- water  gives  i8^ 
better  results  after  the  fifth  year  than  the  same  land  which 
has  been  irrigated  with  clear  artesian  water."  (Wilson's 
**  Manual  of  Irrigation  Engineering.")  Sewage  is  used  for 
irrigation  with  excellent  results. 

QUERIES. 

1.  An  analysis  of  the  sewage  of  Meriden,  Conn.,  showed  4.27 
parts  of  chlorine,  0.840  of  free  ammonia,  0.976  of  albuminoid 
ammonia.  What  was  probably  the  number  of  gallons  of  flow  to  each 
contributor  ? 

2.  If  Newark  had  a  population  of  160,000  in  1892,  what  sum 
could  have  been  paid  by  her  for  the  Pequannock  water-supply  in  4^ 
40-year  bonds,  without  any  net  loss  to  herself,  including  expenses 
of  sickness,  and  counting  each  life  as  worth  $5000  to  her.'' 


CHAPTER    III. 
REQUISITES   OF   A   SUPPLY.     QUANTITY. 

Art.  11.     For  Irrigation. 

For  irrigation  about  one  to  three  cubic  feet  per  year  is 
required  for  each  square  foot  of  irrigated  surface,  varying 
with  the  crop,  the  porosity  of  the  soil,  the  amount  and 
character  of  vegetation  thereon  (as  affecting  evaporation), 
temperature  and  precipitation,  and  the  skill  of  the  irrigator. 
Probably  with  care  2  cubic  feet  should  sufifice  for  the  most 
demanding  crop  on  any  soil.  The  water  required  decreases 
as  the  land  is  cultivated  and  as  the  ground-water  surface 
rises  owing  to  previous  irrigation.  The  quantity  of  water 
used  for  irrigation  is  customarily  stated  in  acre-feet,  one 
acre-foot  being  the  amount  necessary  to  cover  one  acre  one 
foot  deep,  or  43,560  cubic  feet.  The  water  is  not  used  con- 
stantly, but  is  turned  into  the  fields  from  two  to  ten  times, 
or  "  services,"  a  year.  Vegetables  are  generally  given  more 
services  than  grain  or  grass,  requiring  also  a  greater  total 
amount  of  water.  The  quantity  stated  is  for  the  net  area 
irrigated,  and  this  will  probably  average  about  three  iburths 
of  the  total  area  of  a  district.  Of  the  run-off  collected  15  to 
50  or  more  per  cent  will  be  lost  by  evaporation  and  seepage 
from  the  reservoirs  and  canals.  The  number  of  acres  which 
can  be  irrigated  by  the  yield  from  a  given  area  will  there- 

29 


30  WATER-SUPPLY  ENGINEERING. 

fore  be  approximately  the  quotient  obtained  by  dividing  the 
required  depth  of  irrigating  water  (i  to  3  feet)  into  the 
product  of  the  catchment  area  (in  acres),  the  annual  rainfall 
(in  feet),  the  proportion  of  this  collected,  and  the  proportion 
of  this  last  delivered  (generally  about  .75).  Thus,  on  the 
Sweetwater  drainage  area,  in  Southern  California,  the  mean 
rainfall  is  20.64  inches,  average  run-off  9.3^:  the  duty  is  1.6 
acre-feet  per  year.      One  acre  of  watershed  would  therefore 

i       ■  u    ■    ■     .-         f        20.64  X   .093  X   .75         ^^„, 

furnish    irrigation    for    7 =  0.075    acres. 

^  12  X  1.6  ^  ^ 

The  watershed  of  186  square  miles  would  hence  irrigate  13. 9S 
square  miles  or  8928  acres.  In  1896,  4580  acres  were  irri- 
gated and  2600  people  were  dependent  upon  the  reservoir 
for  domestic  water.  (Schuyler,  Eighteenth  Annual  Report 
of  U.  S.  Geol.  Survey.) 

Art.  12.     Population  to  be  Supplied. 

With  very  few  exceptions  American  cities  and  villages 
have  increased  in  population  in  the  past,  and  will  continue  to 
do  so  in  the  future  so  long  as  commercial  and  social  condi- 
tions retain  their  present  character  and  tendencies.  The 
growth  of  the  United  States  follows  very  closely  a  general 
law  of  diminishing  percentage  of  increase,  this  being  for  the 
decade  ending 

1800       l8lO       1820       1830       184O       1850       i860       1870       1880       1890       IQOO 

35.1;?      36.4?^      33.1^      33.5^      32.7^      35.9^       35.6^      22.6,'?       30.1:?       24.9^      20.7,'^ 

that  of  each  of  the  larger  cities  follows  a  uniform  law  with 
fair  regularity;  while  smaller  cities  and  villages  may  follow 
one  law  of  growth  for  a  series  of  years,  when  some  change  in 
condition  may  cause  a  considerable  change  in  the  law.  It 
follows  that  the  future  population  of  a  State  or  large  city  can 
be  predicted  with  more  certainty  than  can  that  of  a  small  com- 
munity. 

The     method     of     predicting     future     growths     generally 


REQUISITES   OF  A    SUPPLY.     QUANTITY. 


31 


32  WATER-SUPPLY  ENGINEERING. 

adopted  is  to  plot  all  past  known  populations,  using  the 
year  as  one  ordinate  and  the  corresponding  population  as  the 
other,  pass  a  curve  as  nearly  through  these  points  as  possible 
and,  finding  its  formula,  project  it  into  the  future  years. 
This  curve  cannot  of  course  return  upon  itself,  but  must 
approach  some  asymptote  as  a  limit.  It  may,  from  unforeseen 
circumstances,  reverse,  even  so  far  as  to  show  a  loss  rather 
than  gain  of  population.  Such  a  curve  for  the  city  of  Balti- 
more is  shown  in  Plate  III. 

If  the  city  is  new,  or  no  population  data  are  available, 
the  future  population  must  be  more  or  less  of  a  guess  pure 
and  simple.  Certain  known  facts  may  assist  this,  however. 
For  instance,  no  modern  city  can  reach  any  considerable  size 
which  is  not  well  served  by  transportation  facilities  such  as 
railroads,  canals,  or  ocean  steamers.  Railroads  and  canals  in 
a  hilly  or  mountainous  country  follow  the  valleys,  and  the 
junction  of  several  valleys,  or  a  good  harbor,  is  hence  a 
locality  favorable  to  a  large  population. 

The  U.  S.  Census  shows  that  the  density  of  population  is 
greatest  on  the  seacoast  and  diminishes  gradually  and  quite 
uniformly  up  to  the  2000-foot  contour,  above  which  the 
population  is  quite  sparse;  more  than  three  fourths  of  the 
population  living  below  the  1000-foot  contour. 

The  table  on  page  33  shows  the  distribution  of  population 
relative  to  altitude,  as  determined  by  the  U.  S.  Census. 

The  necessity  for  estimating  the  future  population  arises 
from  the  fact  that  the  water-works  should  be  of  a  capacity 
sufficient  not  only  for  the  present,  but  for  the  future  also; 
this  being  particularly  true  of  the  supply  of  water.  For  how 
distant  a  future  is  largely  a  matter  of  judgment,  and  depends 
somewhat  upon  the  character  of  the  works;  but  it  is  probable 
that  forty  or  fifty  years  ahead  would  suffice  for  the  majority 
of  cases.  This  would  generally  mean  a  capacity  three  or  four 
times  that  required  for  the  present. 


REQUISITES   OF  A    SUPPLY.     QUANTITY. 


33 


Table  No.  1. 
density  of    population    in    the    united    states    relative   to 

altitude. 
(From  Engineering  News,  vol.  xxvi.  page  71.) 


Altitude  in  Feet. 

Population 
Thousand 

in 
s. 

Population  per 
Mile. 

Square 

Increase  in 

Population  per 

Square  Mile. 

1890 

1880 

1870 

1890 

1880 

1870 

1880  to 
1890 

1870  to 

IS80 

0  to  100 

10,387 

8,273 

6,441 

51.8 

41-3 

32.2 

10.5 

9.1 

ICO  to  500 

13.838 

11,654 

9,240 

35-6 

30.0 

23.8 

5.6 

6.2 

500  to  1000 

23.947 

19.813 

15,914 

43-9 

36.3 

29.1 

7.6 

7.2 

1000  to  1500 

9-431 

7,256 

5,136 

23.8 

18.3 

13.0 

5-5 

5-3 

1500  to  2000 

2.354 

1,597 

978 

9.8 

6.7 

4.1 

3-1 

2.6 

2000  to  3000 

1,154 

723 

405 

4.4 

2.7 

1-5 

1-7 

1.2 

3000  to  4000 

381 

185 

124 

2.1 

I.O 

0.7 

I.I 

0.3 

4000  to  5000 

296 

135 

75 

I.I 

0.5 

0.3 

0.6 

0.2 

5000  to  6000 

487 

270 

137 

2.2 

1.2 

0.6 

I.O 

0.6 

6000  to  7000 

161 

98 

56 

I.O 

0.6 

0.3 

0.4 

0.3 

7000  to  8000 

94 

59 

33 

I.O 

0.6 

0.4 

0.4 

0.2 

8000  to  9000 

43 

39 

14 

I.I 

0.9 

0.3 

0.2 

0.6 

9000  to  10,000 

39 

45 

3 

2.0 

2-3 

0.2 

-0.3 

2.1 

Above  10,000 

10 

9 

2 

0.5 

0.5 

0.1 

0.4 

The  future  population  is  that  within  the  future  limits  of 
the  city,  which  is  not  necessarily  the  area  now  occupied 
The  population  on  any  given  area  will  probably  approach, 
and  in  many  districts  will  have  already  reached,  a  maximum 
limit.  This  may  be  from  thirty  to  sixty  per  acre  in  suburban 
and  the  better  class  of  residence  districts,  and  several  hun- 
dred per  acre  in  crowded  tenement  blocks  of  large  cities. 

Art.  13.     Quantity  for  City  and  Suburban  Use. 

In  a  private  residence  the  water  furnished  is  used  for 
drinking,  cooking,  washing,  and  other  domestic  purposes; 
for  watering  horses  and  cattle,  washing  carriages  and  other 
stable  duties;  and  for  sprinkling  lawns,  flower-beds,  etc. 
The  approximate  quantities  so  used  on  an  American  suburban 
property  probably  average  about  as  follows: 

For  ordinary  indoor  use 15  to  25  gals,  per  capita  per  day. 

"    stable  use 50  to  200  gals,  for  each  horse  and  carriage. 

"  sprinkling  lawns  in  sum-  \  200  to  2000  gals,  per  house  per  day,  during 
mer,  and  wasted  to  pre-  >■  the  coldest  and  dryest  weather — say 
vent  freezing  in  winter.  )      four  months  of  the  year. 


34  WATER-SUPPLY  ENGINEERING. 

For  city  residences,  or  those  having  small  yards,  and 
where  stables  are  few,  a  yearly  allowance  of  20  to  30  gals. 
per  capita  per  day  should  be  ample  for  domestic  use;  i  to  2 
gals,  per  capita  for  stable  use;  20  to  40  gals,  per  capita  for 
office  buildings,  stores,  restaurants,  hotels,  elevators,  fac- 
tories, etc.  ;  for  public  schools,  street-sprinkling,  sewer-flush- 
ing, fountains,  and  extinguishing  fires,  3  to  5  gals. ;  and  for 
losses,  3  to  7  gals. ;  or,  say,  45  to  85  gals,  per  capita  per  day. 
There  may  be  numerous  factories,  breweries,  or  other  indus- 
tries using  large  amounts  of  public  water  which  will  greatly 
increase  this  per  capita  average;  but  the  tendency  is  for  such 
establishments  to  secure  a  private  water-supply,  as  being 
cheaper  for  them  in  the  end.  The  amounts  used  for  various 
purposes  in  Boston  in  1880  and  1892  are  shown  in  the  table 
on  page  35. 

The  figures  given  above — 45  to  85  gals,  per  capita — as 
ample  for  most  cities  are  in  a  great  number  of  cases  exceeded, 
and  in  most  such  cases  the  excess  is  careless  or  wilful  waste. 
The  table  on  page  36  shows  the  consumption  in  a  number  of 
American  cities. 

The  last  two  cities  in  the  list,  with  practically  the  same 
population,  show  extreme  rates  of  consumption.  Nanticoke 
must  waste  at  least  one  half  its  supply;  while  at  Baton  Rouge 
the  low  rate  is  accounted  for  by  the  small  proportion  of  the 
population  using  the  supply.  New  York,  Brooklyn,  Boston, 
St.  Louis,  Salem,  Keokuk,  and  Brookline  show  by  their  1890 
record  that  even  with  some  waste  the  rate  can  be  kept  under 
or  near  75  gals. ;  while  Providence  and  Fall  River  show  that 
with  careful  administration  it  may  be  much  lower  than  this. 
The  great  increase  in  New  York's  rate  between  1890  and 
1897  was  due  to  the  completion  and  use  of  the  new  Croton 
Aqueduct,  furnishing  increased  quantity  and  head  of  water. 
Immediately  before  its  completion  the  rate  had  fallen  to  70 
gals. 


REQUISITES   OF  A    SUPPLY.     QUANTITY.  35 

Table  No.  2. 

consumption  in  gallons  per  capita  for  various  purposes 
from  the  cochituate  works  in  boston  in  1880  and  l8y2. 
(brackett.) 


MANUFACTURE   AND    TRADES 

Office  buildings  and  stores  ..    0.844 

Steam  railroads i-i39 

Sugar  refineries 0.81 1 

Factories,     machine-shops, 

mills,  and  engines '.  0.966 

Iron-works  and  -foundries  .  . ;  0.573 


Population  in  1880,  306,000. 


Metered. 


0.143 
0.324 


0.556 
0.214 


Marble-  and  stone-works 

Gas  companies 

Electric  light  companies 

Breweries 

Oil-  and  chemical-works 

Laundries 

Restaurants 

Stables  

Steamers  and  shipping.. 
Elevators  and  motors  . . . 

Street  railways 

Saloons 

Hotels I   1.454 

Theatres  and  halls 

Markets  and  cellars 

Greenhouses 

Miscellaneous 

Totals 


0.1 29 

0.443 
0.325 
1.033 


DOMESTIC    USES. 

Apartment  hotels 

Dwelling-houses 

Stables  

Hand  hose 

Club-hou.ses , 

Churches 

Miscellaneous 

Totals 


0.314 


9.268 


0.047 


PUBLIC    USES. 

Hospitals 

Schools 

City,  State,  and  Government 

buildings 

Urinals,  fountains,  etc 

Miscellaneous 

Totals 


0.047 


0.505 


0.505 


Un- 
metered. 


0.150 
0.650 


Total. 


11.044 

1. 139 
o.Sii 

3.086 

0.573 
0,143 
0.324 


1.500 
0.150 


0.556 
0.214 
0.150 
0.779 
0.443 
1-325 
I-033 


1.500 
1.604 


0.150 
0.160! 


0.150 
0.160 
0.314 


16.080  25.348 


5.850 
50.000 
1.500 
1.250 
0.040 
0.250 


^58.890 

0.200 
0.400 

0.400 


0.500 


1.500 


5.897 
50.000 
1.500 
1.250 
0.040 
0.250 


58.937 

0.200 
0.905 

0.400 


0.500 


2.005 


Population  in  1892,  430,00^ 


^^'^'^^-  metered.     Total. 


5-63 
2.26 
1.70 

2.15 
0.24 
0.12 

0.75 
0.69 
0.89 
0.19 
0.15 
0.37 
0.60 
0.82 

2.95 
0.90 
0.27 

1-55 
o.  10 


0.27 


22.60 


1.72 


0.18 


1.90 


0.30 
0.30 

0.83 


1-43 


5.54 


0.35 
0.29 


0.08 


0.89 
0.07 
0.09 


0.08 
0.28 


7.67 


12  34 
43-90 
1.38 
2.25 
0.07 
0.18 
0.22 


*6o.34 


0.21 
0.12 


0.52 
0.14 


0.99 


II. 17 
2.26 
1.70 

2.15 
0.24 
0.12 
0.75 
0.69 
0.89 
0.19 
0.50 
0.66 
0.60 
0.90 
2-95 
0.90 
1.16 
1.62 
0.19 


0.08 
0.55 


30.27 

14.06 
43.90 
1.33 
2.25 
0.25 
0.18 
0.22 


62.24 


0.51 
0.42 


1-35 
0.14 


2.42 


*  The  quantity  wasted  is  included  in  the  unmetered  consumption. 


36 


WATER-SUPPLY  ENGINEERING. 


Table  No.  3. 
population  and  per  capita  water  consumption  in  various 

CITIES. 

(See  also  Appendix  A,  Table  No.  74.) 

Consumption  in  Gallons  per  Day. 


Date 

i860 

1870 

1880. 

18  0 

^ 

City. 

c 
0 

a 

0 

s. 
a 

3 
(5 

5 
U 

c 
.0 

"a 

a 
0 

a. 

c 
0 

a 
E 

3 

c 
0 
u 

c 
0 

"5 
a. 
0 

a. 

c 

_o 

0. 

B 

3 

C 
0 

U 

c 

0 

3 
a 

c 

0 

a 

e 

3 

c 
0 
U 

c 

_o 

"a 

a 
0 

0- 

c 
0 

a 

S 

3 

c 
0 
U 

c 

3 

0. 

0 

0. 

c 
2 

0. 
S 
3 

c 
0 
U 

1,206,590 
503,185 
847,170 
566,663 
413,700 
350,518 
255,139 
160,146 
116,340 
104,857 
48,961 
27,563 

77 
112 

68 
54 
87 
72 
76 
65 
130 
34 
30 
55 

1,515.301 

1,099,850 
1.046.964 

853.945 
527.630 

45'.770 

296,908 

261,353 

205,876 

132,146 

74,308 

30.801 

20,056 

18.060 

14,101 

12,103 

10,478 

10,044 

85 
127 
132 
67 
80 
78 
115 
106 
155 
46 
28 

69 
22 

194 
78 
73 
19 

199 

1,700,000 

Chicago 

PhiLidelphia 

29,963 
121,376 
96,838 
139,800 
77,860 

"5.435 
17,034 
21,019 
41.513 
11,524 
20,264 

42 
20 

112,172 

565,529 
266,661 
177,900 
160,773 
161,044 

43,417 
45,619 
50.666 
14,026 
22,252 

43 
36 
12 
97 

30 
14 
52 

298,997 
674,022 
396,099 
312,171 
310,864 
216.039 
92,829 

79,577 
68,904 
26,766 
24,117 

73 

55 
47 
60 
35 
48 
3' 
64 

31 

1,385,734 

215 
80 

279,107 

125 

Fall  River 

l«S 

Wilmington,  N.  C.  . 

1 

The  consumption  in  a  number  of  English  cities  in  1897 
was  as  follows: 

Table  No.  4. 
water  consumption  in  english  cities  in   1897. 


City. 


Worcester 

Wigan 

Plymouth 

Swansea 

Middlesborough 

Sheffield 

Manchester 

Average  of  thirty-six  cities 


Population. 


45,000 
60,000 

9S.575 
100,000 

187,331 
415,000 

849-093 


Consumption, 
Gallons  per  Day, 


43 
20 

59 
35 
61 
21 
40 
33 


The  rates  in  these  tables  are  obtained  by  dividing  the 
total  consumption  by  the  total  population.  A  larger  per- 
centage than  formerly  of  each  city's  population  now  uses  the 


EEQUISITES    OF  A    SUPPLY.     QUANTITY. 


17 


public  supply,  and  the  number  of  faucets,  bath-tubs,  water- 
closet  flushes,  etc.,  in  each  house  is  greater  than  formerly; 
also  more  water  is  used  for  flushing  sewers,  public  fountains, 
etc.  ;  and  these  facts  to  a  large  extent  account  for  the 
increasing  rate  ot  consumption  in  many  towns.  This  increase 
in  fixtures  in  Boston  is  shown  by  Table  No.  5.  (Brackett, 
Transactions  American  Society  of  Civil  Engineers,  vol 
XXXIV.  page  203.) 

Table  No.  5. 

NUMBER    OF    WATER-FIXTURES    IN    USE    AND    FIXTURES    PER    CAPITA, 
ETC.,    ON    COCHITUATE    WORKS,    FROM     1870    TO     1892. 


Name  of  Fixture. 

1870. 

u    ■ 

I" 

1880. 

4J     ■ 

at  «J 
c  t 

1890. 

-J 

1891. 

Taps 

5,893 
53,010 
23,961 

8,892 
25,050 

2,447 

9,615 

547 

723 

73 

13 

56.6 
59-4 
925 
93-8 
107.7 
65.1 
99.1 

-  63-9 
32.2 
90.4 

—  lOO.O 

9,228 
84,498 
46,116 
17,230 

52,030 
4,041 

19,139 
197 
956 
139 

61.7 

39-7 
39-8 
85.2 
75-4 
20,7 

T26.  7 

-   81,7 

56.2 

101.4 

14,922 

118.066 

64,462 

31,914 

91,280 

4,879 

43,389 

36 

1,493 

280 

12.0 
6.0 
6.2 

'7-5 
12.5 

-  2.6 
23.0 

-  50.0 

-  4,1 

-  7.1 

16,706 

Bowls     

68,448 

37,495 
102,687 

Bath-tubs 

4,754 

S3, 360 

18 

Private  hydrants 

Foot-baths 

Hydraulic  rams 

',432 
260 

Totals 

130,234 

79-3 

31-7 

72.2 

36.2 

310 

-     3-9 

233,574 

58.7 

370,721 

10.7 

Total  population 

Daily      average       con- 

250,500 

16,257,700 
0.520 
64.9 
124.8 

330,000 

28,000,000 
0.708 
85.0 
119. 9 

24.4 

21 .0 

37-5 

-  2.9 

-  23.8 

410,600 

33,871,700 
0.903 
82.5 
91.4 

4.8 

22. 0 

5.6 

16.4 

10.5 

430,200 

Fi.xtures  per  capita 

Consumption  pr.  capita 
Consumption  pr. fixture 

0.954 
96.0 
101 .0 

The  consumption  so  far  referred  to  is  the  average  daily  con- 
sumption ;  the  actual  daily  consumption  will  vary  from  month 
to  month,  week  to  week,  and  day  to  day.  The  maximum 
consumption  will  generally  be  in  the  dryest  summer  weather. 
A  maximum  rate  in  urban  districts  may  occur  in  very  cold 
winters,  due  to  waste  through  faucets  to  prevent  freezing. 
Table  No.  6  gives  the  average  monthly  rates  for  several 
cities. 

For  some  purposes  it  is  desirable  to  know  the  maximum 
rates  of    consumption;    and    Table    No.    7    gives    these    for 


38 


WATER-SUPPLY  ENGINEERING. 


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WA  TER-SUPPL  V  ENGINEERING. 


several  places  for  the  month,  week,  day,  and  hour,   in  per- 
centages of  the  average  rate  for  the  year  in  question. 

The  maximum  rate  of  consumption  at  any  one  point  will 
probably  be  that  due  to  use  for  extinguishing  fires.  The 
annual  rate  per  capita  for  fire  purposes  will  probably  be  about 
0.08  to  0.12  gals,  per  day;  but  the  rate  during  use  will  be 
much  greater  than  this.  The  number  of  fire-streams  of  175 
to  250  gals,  per  minute  each  required  simultaneously  in 
American  cities  of  various  magnitudes  is  considered  by  differ- 
ent authorities  to  be  as  follows: 

Table  No.  8. 

number  of  fire-streams  required    simultaneously    in    cities 
of  various  magnitudes. 


Population. 

Freeman. 

Shedd. 

Fanning. 

Kuichling. 

Gallons  per 

Minute 
by  Freeman. 

2-3 

(4-6) 

4-8 

6-12 

8-15 

12-18 

(14-20) 

15-22 

20-30 

(24-36) 

(27-40) 

30-50 

3 
6 
6 

9 
12 

18 
20 
22 
23 
34 
38 
40 

35c^750 

700-1500 

700-2000 

1050-3000 

140(^3750 

2100-4500 

2450-5000 

2625-5500 

3500-7500 

4200-QOOO 

4725-10000 

5250-12500 

4,000 
5,000 
10,000 
20,000 
40,000 
50,000 
60  000 

7 

5 

7 

10 

14 

10 

14 

17 
22 

100,000 
150,000 
180  000 

18 
25 

30 

200,000 

One  of  the  benefits  of  a  public  water-supply  is  the  fire 
protection  afforded,  and  unless  this  is  ample  the  system  is 
lacking  in  one  of  its  essential  functions.  This  affects  not 
onlv  the  possibility  of  extinguishing  fires,  but  also,  on 
account  of  this,  the  rates  of  fire  insurance  throughout  the 
city;  and  in  most  cases  the  interest  on  the  cost  of  ample 
provision  for  such  service  will  be  more  than  covered  by  the 
reduction  in  insurance  rates. 


requisites  of  a  supply.    quantity.  4^ 

Art.  14.     Waste  of  Water. 

There  are  very  few  cities  in  which  a  yearly  average  of  75 
gals,  per  capita  per  day  is  not  sufficient  for  all  uses,  and  in 
most  cities  where  the  consumption  exceeds  this  it  might  be 
brought  within  this  limit  by  proper  treatment.  This  being 
the  case,  it  is  evident  that  there  must  be  a  great  amount  of 
water  wasted  in  many  cities.  In  New  York  City  this  appears 
to  be  about  40  gals.,  in  Detroit  50,  and  in  Philadelphia  more 
than  140  gals,  per  capita  daily.  If  the  supply  is  pumped, 
this  means  increased  expense  for  coal-consumption  and  en- 
largement of  pumping-plant ;  if  the  supply  is  from  wells  or 
reservoirs,  it  hastens  the  day  when  new  wells  must  be  sunk 
or  new  drainage  areas  sought;  and  in  any  case  it  means  that 
either  the  mains  must  be  unnecessarily  large  or  the  pressure 
will  be  decreased  below  that  desired.  Millions  of  dollars  are 
being  spent  by  many  of  our  larger  cities  to  so  increase  their 
supply  that  two  thirds  of  it  may  be  wasted. 

This  waste  is  either  intentional,  careless,  or  through 
ignorance.  Under  intentional  waste  may  be  classed  the 
opening  of  faucets  on  winter  nights  to  prevent  freezing  of 
poorly  located  plumbing;  the  lavish  sprinkling  of  lawns  and 
streets  in  summer;  and  unnecessary  amounts  used  in  auto- 
matic sewer  flush-tanks,  as  well  as  in  automatic  water-closet 
flushes  in  hotels  and  office  buildings.  Carelessness  usually 
takes  the  form  of  non-attention  to  leaky  house-fixtures, 
thousands  of  which  can  be  found  in  almost  any  city.  More 
or  less  leakage  in  every  system  defies  detection,  being  prob- 
ably the  result  of  very  slight  leaks  in  thousands  of  joints,  in 
fire-hydrants,  stop-valves,  corporation-cocks,  and  other  por- 
tions of  the  distributing  system.  This  has  been  found  to  be 
5  to  10  per  cent  of  the  consumption  in  some  cities. 

The  winter  waste  due  to  the  first-mentioned  cause  is 
shown  in  Table  No.  6.      In  Rock  Island  this  was  greatest  in 


42  WATER-SUPPLY  ENGINEERING. 

January  and  February;  in  New  England,  Brooklyn,  and 
Rockford,  111.,  in  February.  In  Rockford  the  February 
consumption  is  seen  to  be  about  8^  greater  than  that  of  the 
other  two  winter  months.  Daily  records  would  show  this 
waste  much  more  prominently.  At  Reading,  Pa.,  the  maxi- 
mum winter  rate  during  1897-98  was  on  Dec.  10,  being  125^ 
of  the  average  for  that  year.  At  Newton,  Mass.,  during 
twenty  years  past  the  winter  weekly  maximum  has  fallen  in 
December  four  times,  in  January  four  times,  and  in  February 
nine  times;  the  greatest  excess  being  in  the  second  week  of 
December,  when  the  average  consumption  for  the  week  was 
122^  of  the  annual. 

The  summer  waste  is  more  prominent,  the  average  con- 
sumption during  June,  July,  and  August  running  from  4  to 
15  per  cent  above  the  yearly  average. 

The  waste  of  water  by  the  city  in  flushing  sewers  by 
automatic  tanks  is  in  some  cases  most  excessive.  From  500 
to  800  gals,  per  day  per  tank  should  be  sufficient  for  the 
proper  maintenance  of  a  lateral  sewer;  but  carelessness  or 
ignorance  has  been  known  to  cause  ten  to  thirty  times  this 
amount  to  be  used.  The  Water  Company  of  Racine,  Wis., 
found  the  iii  flush-tanks  of  that  city  using  1,436,429  gals,  per 
day,  an  average  of  about  13,000  gals,  each — an  actual  waste 
of  certainly  more  than  1,000,000  gals,  per  day.  Street-sprink- 
ling is  also  a  common  cause  of  much  waste,  one  Massachusetts 
city  using  7^  of  its  entire  supply  for  this  purpose  in  1897. 

The  loss  through  leaky  house-fixtures  is  enormous. 
"  From  10  to  15  per  cent  of  the  premises  examined  in  Boston 
are  found  to  have  defective  fixtures,  and  of  12,609  defective 
fixtures  reported  in  1893,  7314  were  ball-cocks.  The  tank 
ball-cock  is  without  doubt  the  source  of  the  greater  part  of 
the  waste  from  defective  plumbing."  (Dexter  Brackett, 
•*  Consumption  and  Waste  of  Water,"  Transactions  American 
Society  of  Civil  Engineers,  vol.  xxxiv.  page  196.)     In  1897 


REQUISITES   OF  A    SUPPLY.     QUANTITY.  43 

there  were  92  ii  defective  fixtures  on  47,778  premises  in 
Boston,  and  1600  leaks  on  4651  metered  services.  Of  the 
latter,  959  were  ball-cocks  and  valves,  521  were  sink-,  hopper-, 
bowl-,  and  bath-faucets,  and  120  were  burst  service-pipes. 

In  Philadelphia,  of  782  appliances  in  a  certain  section 
containing  539  population,  22  were  leaking  slightly,  and  32 
were  running  continually;  and  it  was  found  in  one  district 
that  63^  of  the  water  furnished  was  wasted  by  I'jio  of  the 
consumers,  and  in  another  86^  was  wasted  by  7$^  of  the 
consumers;  this  being,  not  lavish  use,  but  absolute  waste. 

A  leaky  faucet  may  waste  75  to  300  gals,  per  day,  and  a 
leaky  ball-cock  may  easily  permit  1000  gals,  per  day  to  pass 
it.  Unless  this  leakage  inconveniences  the  householder  he 
will  seldom  repair  the  defective  fixtures  if  not  compelled  to. 
The  greatest  amount  of  leakage  of  this  class  is  generally 
found  in  rented  houses,  particularly  of  the  poorer  class,  where 
the  plumbing  is  cheap,  and  money  for  repairing  a  leak  is  spent 
grudgingly. 

Aside  from  these  there  are  many  unknown  sources  of 
waste;  generally,  leaking  mains  or  house-connections.  Differ- 
ent authorities  consider  that  an  average  of  500  to  3000  gals, 
leaks  through  pipe-joints,  hydrants,  and  valves  on  each  mile 
of  pipe  in  a  well-constructed  system  which  has  been  in  use 
for  some  years;  the  leakage  being  generally  so  small  at  any 
one  point  as  not  to  be  detected.  Although  in  Boston  broken 
4-  and  6-inch  pipes  leaking  looo  to  4000  gals,  per  hour  have 
gone  for  years  undiscovered;  and  other  cities  have  un- 
doubtedly had  similar  experiences. 

Most  commercial  articles  are  sold  by  the  quantity,  and 
there  seems  to  be  no  good  reason  why  water  also  should  not 
be.  "  Water  should  be  free  as  air,"  the  catch-word  in  many 
cities,  may  be  true;  but  its  distribution  should  not  and  can- 
not be,  nor  would  this  be  expected  if  a  cart  instead  of  pipes 
were  the  distributing  medium. 


44 


J'VA  TER-SUPPL  Y  ENGINEERING. 


Art.  15.     Statistics. 

The  following  water-works  statistics  are  added  as  of 
interest  in  this  connection,  although  not  requiring  special 
discussion. 

Table  No.  9. 

PERSONS    PER    DWELLING    IN    VARIOUS    CITIES. 


1870. 

1S80. 

1890. 

City. 

Persons 

Persons 

Persons 

Population. 

to  a 
Dwell- 
ing. 

Population. 

to  a 

Dwell. 

ing. 

Population. 

to  a 
Dwell- 
ing. 

New  York,  N.  Y. . . . 

942,292 

14.72 

1,206,299 

16.37 

1,515.301 

18.52 

Philadelphia,  Pa.... 

674,022 

6. or 

847,170 

5-79 

1,046,964 

5.60 

Brooklyn,  N.  Y 

396,099 

8.64 

566,663 

9. II 

298,977 
250,526 

6.70 
8.46 

503,185 
362,839 

8.24 
8.26 

1,099,850 

8  60 

Boston,  Mass 

St.  Louis,  Mo 

310,864 

7. 84 

350,518 

8.15 

451.770 

7.41 

Baltimore,  Md 

207,354 

6.63 

332,313 

6.54 

Cincinnati,  O 

216,239 

8.81 

255.139 

9. II 

296,908 

8.87 

San  Francisco,  Cal. . 

149.473 

5-77 

233,959 

6.86 

New  Orleans,  La. . . . 

191,418 

5-69 

216,090 

5-95 

242,039 

5.63 

Cleveland,  O 

92,829 

5-56 

160,146 

5.89 

261,353 

5-96 

Pittsburg,  Pa 

86,076 

6.05 

156,389 

6.44 

238,617 

6.33 

Buffalo,  N.  Y 

117,714 

6.44 

155,134 

6.55 

255.664 

6.86 

Washington,   D.  C  . 

109,199 

5.59 

147,293 

6. II 

Newark,  N.  J 

105,059 

7-32 

136,508 

7.26 

181,830 

7.81 

Louisville,  Kv 

100,753 

6.87 

123,758 

6.55 

161,129 

6.45 

Jersey  City,  N.  J. . . . 

82,546 

8.37 

120,722 

8.59 

163,003 

8.78 

Detroit,  Mich 

79.577 

5.42 

116,340 

5.68 

205,876 

5-57 

Milwaukee,  Wis  .... 

71,440 

5-48 

115. 5S7 

6.17 

204,468 

6.22 

Providence,  R.  I. . .  . 

68,904 

7.46 

104,857 

7.41 

Albany,  N.  Y 

69,422 

7.94 

90.758 

6.85 

Rochester,  N.   Y. .  .  . 

62,386 

5-36 

89,366 

5.65 

Allegheny.    Pa 

53.180 

6.37 

78,682 

6.59 

105,287 

6.36 

Indianapolis,  Ind.. .  . 

48,244 

6.17 

75.056 

5-47 

105.436 

4.99 

Richmond,  Va 

51,03s 

6.35 

63,600 

6.67 

New  Haven,  Conn-- 

50,840 

6.28 

62,882 

6.31 

Lowell,  Mass 

40,928 

6.43 

59,475 

7.21 

Kansas  City,  Mo. . . . 

32,260 

5.95 

55,785 

6.48 

132,716 

5.74 

Charleston,  S.  C.  .  •  . 

48,956 

714 

49,984 

7-63 

Scranton,  Pa  

35,092 

6.21 

45,850 

6.25 

Lawrence,    Mass.... 

28,921 

8.40 

39.151 

8.50 

35.629 
33,592 

6.75 
4.68 

Memphis,  Tenn 

40,226 

6.23 

29,910 
24,966 
21.915 

5-85 
6.70 

Norfolk     Va 

Holyoke,  Mass 

10.52 

Springfield    111 

19.743 

5 -60 

REQUISITES    OF  A    SUPPLY.     QUANTITY.  45 

Tadle  No.  10. 

population  per  mile  of  mains  and  per  tap,  cost  of  systems 
per  mile  of  main,  and  pressure  in  mains  in  pounds  ; 
averages  for  the  united  states  in  1 888. 


New  England  . 

Middle 

South  Atlantic. 
South  Central  . 
North  Atlantic 
Northwestern  . 
Southwestern  . 
Pacific 


Average 


Population 
per  Mile 
of  Main. 


455-4 

830.0 
713.6 
780.1 

597-7 
467-3 
563-1 
276.0 


5S5.4 


Population 
per  Tap. 


7-6 

6.9 

II. I 

13-4 

8-5 

12. 1 

9.4 

6.1 


9.4 


Cost  per 
Mile  of  Main, 


Bi6,8oo 
21,000 
13.070 
20,650 
13.780 
15,660 
21,580 
19,800 


i7,8oof 


Pressure  * 
in  Mains. 
Pounds. 


30-100 

30-110 

30-90 

30-90 

30-100 

20-90 

30-90 

20-gO 


30-90 


*  80  per  cent  of  each  district  is  within  the  limits  given.  The  actual  ran<;e  is  from  10  to 
180  pounds. 

t  Except  a  few  large  cities,  very  few  plants  cost  more  than  $20,000  per  mile,  and  few  less 
than  $10,000. 


Table  No.  11. 

number    of    taps   and    meters,  and    miles   of    pipes  ;    several 
CITIES  ;  1897. 


City. 


New  York,  N.  Y.  . 
Philadelphia,  Pa.  . 

Boston,  Alass 

St.  Louis,  Mo 

Detroit,  Mich 

Providence,  R.  I. . . 
Indianapolis,  Ind.. 
■Charleston,  S.  C... 

Reading,  Pa 

Yonkers,  N.  Y.  . . . 

Augusta,  Ga 

Taunton,  Mass.... 

Canton,  O 

Leavenworth,  Kan 
Burlington,  Vt.  . .  . 

Ogden,  Utah 

El  Paso,  Tex 

Middleboro,  Mass. 
■Charlottesville,  Va 
"Wellesley,  Mass. . . 

Ocala,  Fla 

Alexandria,  La.  . .  . 

Elgin,  Minn 

Garfield,  Wash 


Population. 


,700,000 

.3S5.734 

527,630 

451,770 

205,876 

132,146 

110,000 

55.000 

74.410 

32,033 

33.300 

25.448 

26,189 

19,768 

14,590 

14,889 

10,338 

6065 

5591 
3600 
2904 
2S61 

885 
317 


Per  Capita 
Consump- 
tion. 


112 
187 

80 

78 
155 

46 

81 

28 

87-1 
100 
115 

45 
no 
150 

60 
265 

55 

35 
100 

48 

40 
5 
4-5 

28 


No.  of 
Taps. 


120,000 

221,860 

70,879 

53.354 

48,918 

18,695 

7,000 

1.500 

14,860 

3  714 


3,843 

3,900 

1,440 

2,969 

1,800 

800 

697 

871 

685 

266 

55 

25 

30 


No.  of 
Meters. 


32,329 
1.273 
4.398 
3,979 
4,000 

13.763 
500 

25 

432 

3-706 

62 

1,366 

20 

450 

1,261 

65 

450 

256 

3 
656 

3 
o 
6 
o 


Miles  of 
Distribut- 
ing Pipes. 


750 
II74 

596 
462 
501 
294 

157 

33 
88 

56.7 

44 

71.0 

48 

27 
36.0 

32 
10 

14 

28 
26 

7-5 

7 

i± 

1.2 


46 


WATER-SUPPLY  ENGINEERING. 


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REQUISITES   OF  A    SUPPLY.     QUANTITY. 

Table  No.  13. 

consumption  ;  new  england  cities  ;  1896. 

(Journal  N.  E.  W.  W.  Ass'n.) 


47 


Estimated 
Population. 

Quantity  Used 

through  Meters 

in  Gallons. 

•0 

c 
0. 

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3 

Gallons  pe 

r  Day. 

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Name  of  City 
or  Town. 

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Attleboro,  Mass 

8,500 

6,500 
14,000 

1 

"5,559,540 

53,762,4121  52.977,831 

3i5,6'2 
2,758,261 

37-1 
83.0 

485 
1,484.0 

Bay  City,  Mich 

33.000 

20,000 

10.57 

197 

0 

Brocton,  Mass 

35,000 

32,000 

31,000 

116,536,470 

40,604,662 

1,087,111 

31.06 

34 

qo 

239.80 

Burlington,  Vt 

17,300 

16,900 

16,700 

107,786,961 

18.291,510 

835,565 

48.0 

SO 

0 

272.0 

Fitchburg,  Mass 

26, 500 

23,000 

20,300 

56,900,000 

279.000,000 

94-0 

670.0 

Lynn,  Mass . 

69,361 

07.>39 

249,906,830 

4,551.789 

67 

8 

Middleboro,   Mass. -j 
New  Bedford,  Mass. 

*4,2oo 

3,700 
45,570 

50.25 
89.0 

57 
108 

292.0 
623.0 

5Q.OOO 

4y-530 

40,475,088 

316,760,610 

5,259,017 

0 

I 5 . 500 
29,500 

15.000 
29.100 

14.500 
28,900 

1, 385-134 
1,812,484 

So  0 

95 
62 

5 
7 

505.0 

289.0 

Newton,  Mass 

275,000,000 

55,000,000 

61.4 

Oberlin.  0 

4,600 

3.500 

2,000 

6,000.000 

1,900,000 

33.0 

67,200 

14.6 

33 

6 

143.0 

Readintj,  Mass.  .    . . 

4.750 

4,160 

3.600 

5,545,170     1,031,483 

'99,273 

41.95 

47 

So 

245.41 

Springfield,  Mass.. . 

54.at2 

48.800 

42.500 

372.253,326 

21.0 

4,819.828 

88.0 

113 

0 

581.0 

Taunton,  Mass 

27,093 

26, 700 

26,361 

51,276.720!  02,735,534 

1,167,863 

43.0 

44 

0 

29D.0 

Wahham.  Mass..   . . 

21,500 

21,000 

20,500 

33.441,260 

1,521,133 

70.0 

72 

0 

490.0 

28,500 
40,000 

26,500 
34,000 

708,227 
3,331,802 

24.9 
83.0 

-6 

7 
0 

359 -o 
910.0 

Yonkers,  N.  V. . 

33,000 

248,223,254  365,141,844 

50.3 

100 

*  Fire  district. 


Art.  10.     Summary.     Quantity  to  be  Provided. 

For  domestic  use  30  to  50  gals,  per  capita  per  day  should 
be  sufficient;  and  where  manufacturers  and  other  similar 
consumers  use  large  amounts,  these  will  seldom  bring  the 
total  of  water  used  above  60  to  85  per  capita.  In  many  cases 
these  limits  are  not  reached ;  and  in  none  should  they  be 
exceeded,  with  proper  management.  If,  however,  a  large 
amount  of  water  is  permitted  to  be  wasted  there  is  no  limit 
to  the  possible  consumption,  but  this  may  reach  300  or  even 
1000  per  capita.  The  most  abundant  supplies  are  generally 
those  requiring  pumping,  and  the  cost  of  reservoirs,  pipes, 
etc.,  as  well  as  of  pumps  and  fuel,  increases  with   the  con- 


48  WA  TEE-SUPPLY  ENGINEERING. 

sumption.  A  rate  of  lOO  gals,  per  capita  should  be  sufficient 
allowance  for  ayiy  ordinary  case,  and  the  consumption  should 
be  kept  within  this  limit  unless  the  supply  can  be  increased 
at  a  less  cost — including  pumps,  reservoirs,  pipes,  and  all 
features  of  the  system — than  that  of  limiting  the  waste  by 
inspectors  and  meters. 

The  average  rate  for  the  year  is  exceeded  by  15  to  30  per 
cent  during  certain  months,  and  50  to  200  per  cent  during 
certain  days  or  hours.  A  large  part  of  this  increase  is  in 
most  cases  wasteful,  but  unless  waste  is  strictly  prevented  an 
allowance  should  be  made  for  variations  in  monthly  rates  (see 
Table  No.  6,  page  38);  and  the  maximum  daily  rate  may  be 
made  50^  greater  than  the  monthly,  which  maximum  will,  in 
residential  districts,  occur  most  frequently  on  wash-days. 

For  periods  of  a  few  minutes  or  hours  still  higher  rates 
may  be  occasioned  by  fires.  Table  No.  8,  page  40,  shows 
the  number  of  streams  which  may  be  required  simultaneously^ 
the  discharge  of  each  of  which  will  generally  be  at  the  rate 
of  250,000  to  360,000  gals,  per  day.  For  a  city  of  10,000, 
for  instance,  this  would  temporarily  increase  the  rate  by 
1,500,000  to  4,320,000  gals.,  or  150  to  432  gals,  per  capita 
per  day;  and  the  rates  thus  increased  must  be  in  every  way 
provided  for  if  ample  fire  protection  is  to  be  furnished.  But 
the  total  annual  rate  is  not  appreciably  affected  by  this. 

QUERIES. 

3.  If  the  maximum  hourly  consumption  at  Detroit,  Mich., 
given  in  Table  No.  7  was  during  the  largest  fire  allowed  for  in 
Table  No.  8,  what  percentage  of  the  average  rate  was  the  domestic 
consumption  at  that  time  ? 

If  the  maximum  hourly  rate  given  for  Boston  was  not  during  a 
fire,  what  would  be  the  total  maximum  rate  to  be  provided  for  ? 

4.  If  each  fixture  in  Boston  leaked  at  the  rate  of  two  drops  per 
second  during  the  year  1892,  what  would  have  been  the  per  capita 
consumption  if  all  leaks  had  been  stopped  ? 


REQUISITES   OF  A    SUPPLY.     QUANTITY.  49 

5.  Judging  from  Table  No.  10,  which  part  of  the  country  was,  in 
1888,  most  liberally  provided  with  water  for  domestic  use  ? 

Allowing  one  tap  to  each  dwelling,  and  an  extra  factory  tap  to 
each  75  inhabitants,  find  from  Tables  9  and  11  the  rate  of  consump- 
tion per  actual  consumer  in  each  of  the  cities  mentioned  in  both 
tables;  using  the  "  persons  to  a  dwelling  "  in  1880  as  still  applicable 
in  1897. 


CHAPTER    IV. 
SOURCES   OF   SUPPLY. 

Art.  it.     Rain. 

In  the  temperate  and  frigid  zones  rain  (and  snow,  which 
is  generally  included  under  this  term  unless  otherwise  speci- 
fied) alone  is  considered  as  the  source  of  water.  For  the  use 
of  man,  whether  for  domestic  or  manufacturing  purposes  or 
for  irrigation,  the  rain,  since  it  does  not  fall  continuously, 
must  be  caught  and  stored  to  tide  over  periods  of  longer  or 
shorter  duration  between  rainfalls.  Nature  performs  this  to 
a  considerable  extent  through  the  agency  of  porous  soil  and 
rocks,  underground  caverns,  lakes  and  ponds,  glaciers,  and 
in  other  ways;  man,  by  the  use  of  cisterns  and  larger  reser- 
voirs, and  to  a  small  extent  by  the  storing  of  ice.  The 
amount  of  rain  which  falls  directly  into  a  reservoir  is  generally 
but  a  small  part  of  its  capacity;  but  it  is  that  which  flows 
from  some  drainage  area,  whether  a  roof  or  a  watershed  of 
thousands  of  acres,  which  gives  the  most  of  the  supply.  If 
this  drainage  area  is  the  surface  of  the  ground,  the  run-off  or 
yield  is  called  surface-water;  but  if  collected  from  an  artificial 
surface  it  is  considered  solely  as  rain-water.  Water  is  col- 
lected in  the  latter  way  and  stored  in  cisterns  in  many  low, 
flat  countries  or  those  with  very  porous  soils,  where  the 
hungry-  soil  yields  none  of  the  rain  as  surface-water,  or  where 
there  are  no  natural  basins  for  impounding  it.  Many 
Southern  cities  in  our  own  country  and  the  adjacent  countries 

50 


SOC/KCES    OF  SUPPLY.  51 

and   islands  rely  almost  wholly  upon  the  collection  of  water 
from  the  roofs  of  dwellings  and  other  buildings. 

Art.  is.     Surface-water. 

By  the  "  yield  "  or"  run-off  "  of  a  catchment  area,  which 
constitutes  surface-water,  is  meant  the  total  amount  of  water 
which  flows  from  a  given  drainage  area,  generally  in  the 
shape  of  streams  fed  by  the  rainfall  upon  this  area.  This  is 
never  the  whole  of  such  rainfall. 

In  falling,  some  rain  is  intercepted  by  the  foliage  and 
stems  of  trees  and  smaller  plants,  to  be  later  evaporated  back 
again  into  the  air.  Of  that  which  reaches  the  earth,  a  part 
flows  over  the  surface  and  the  remainder  enters  the  soil.  If 
the  soil  be  very  porous,  almost  all  the  rain  reaching  it  may  be 
absorbed;  if  non-porous,  little  may  enter  it.  All  soil,  even 
the  densest  rocks,  will  absorb  some  water,  however.  As  the 
unabsorbed  water  flows  over  the  surface  to  the  lower  levels  it 
increases  in  volume  and  forms  into  rivulets,  these  unite  lo 
form  larger  streams,  and  the  river  formed  from  the  union  of 
thousands  of  such  finally  enters  the  ocean.  (Exceptions  will 
be  referred  to  later,  where  streams  are  wholly  evaporated ; 
also  others  where  they  enter  the  ground  and  emerge  into  the 
ocean  far  from  the  shore  and  at  a  considerable  depth.) 

After  a  rain  has  ceased  the  streams  carry  less  and  less 
water,  but  those  of  any  size  seldom  become  entirely  dry, 
even  though  weeks  may  elapse  between  rainfalls  and  the  sur- 
face of  the  ground  become  dry  and  dusty.  The  immediate 
supply  during  this  time  cannot  be  the  rain;  but  is  found  to 
be  that  portion  of  previous  rainfalls  which  was  absorbed  by 
the  earth  and  which  is  now  being  yielded  slowly.  In  general, 
the  more  porous  the  soil  the  more  water  it  will  receive  for 
this  purpose  during  a  given  time  of  rainfall;  and  the  finer  its 
grain  the  more  slowly  will  its  supply  be  yielded  and  become 


52  WATER-SUPPLY  ENGINEERING. 

exhausted.  In  some  instances  the  ground-flow  does  not 
reach  the  same  stream  as  does  the  surface-flow,  but  is  carried 
by  the  dip  of  the  strata  into  another  valley,  as  in  Fig.  i. 


Fig.   I. — Ground-water  Diversion  by  Inclined  Strata, 

The  ground-flow  frequently  emerges  as  springs;  but  the 
larger  part  of  it  ordinarily  reaches  the  stream  as  a  general 
exuding  from  the  banks  and  in  some  cases  the  bottom  of  the 
channel. 

A  study  of  the  material  and  dip  of  the  strata,  and  of  the 
surface  conditions — slope,  vegetation,  existence  of  ponds, 
etc., — as  well  as  of  the  rainfall  and  other  meteorological  condi- 
tions, is  necessary  for  forming  any  estimate  as  to  the  probable 
amount  and  rate  of  yield  of  a  given  watershed,  where  the 
actual  measurement  of  this  is  impossible.  Such  measure- 
ment, to  be  of  value,  should  be  continued  for  a  series  of 
years. 

The  total  amount  of  rainfall  reaching  the  ground  is  not 
yielded  by  the  combined  surface-  and  ground-flow;  a  large 
part  is  evaporated  from  the  surface  and  from  ponds  or  other 
bodies  of  water,  large  or  small;  considerable  is  taken  up  by 
the  vegetation,  which  frequently  sends  its  roots  several  feet 
into  the  soil  in  search  of  it,  the  greater  part  of  this  being 
later  evaporated  from  the  foliage;  and  part  is  held  in  the  soil 
by  capillary  attraction.  Probably  none  of  the  precipitation 
settles  into  the  lowest  strata  which  have  no  outlet,  since 
these  were  filled  ages  ago.  But  if  man  removes  water  from 
these  strata  by  deep  wells,  the  amount  thus  withdrawn  must 
be  replenished.  From  many  watersheds  in  the  Atlantic  and 
Gulf  States    the  ground-water  travels  hundreds  of  miles  to 


SOL'A'C£S    OF  SUPPLY.  53 

emerge  in  the  ocean-bed  far  from  shore;  as  off  the  coast  of 
South  Carolina,  east  of  Matanzas  Inlet,  Fla.,  and  off  the 
shore  of  Pensacola,  Fla. ;  which  water  must  be  withdrawn 
from  the  yield  of  these  watersheds. 

Art.  19.     Rivers  and  Lakes. 

The  dividing-line  between  surface-  and  river-supplies  is  an 
indefinite  one;  but  where  the  supply  is  taken  directly  from  a 
river  or  lake  without  impounding  or  storage,  this  should 
undoubtedly  be  called  a  river-  or  lake-supply.  The  condi- 
tions are  in  many  respects  similar  to  those  affecting  surface- 
waters;  but  the  supply  is  generally  somewhat  more  constant 
and  of  greater  volume,  owing  to  the  larger  drainage  area;  it 
is  more  likely  to  be  polluted,  and  to  lie  lower  relative  to  the 
point  of  utilization. 

Lakes  are  nature's  regulators  of  flow,  and  take  the  place 
of  artificial  storage-reservoirs,  besides  contributing  to  the 
self-purification  of  river-waters.  They  are  generally  but 
enlargements  of  a  river-channel;  although  some  lakes  are 
formed  directly  from  surface-flow  or  from  large  springs,  and 
form  the  sources  of  rivers;  while  still  others  have  ground- 
water as  both  source  and  outlet.  Lakes  can  in  most  cases 
be  relied  upon  as  more  constant  than  rivers  in  both  the 
quantity  and  the  quality  of  water  available. 

Art.  20.     Underground  Supplies. 

The  water  flowing  underground  towards  a  surface  stream 
or  the  ocean  may  emerge  as  springs  or  be  reached  by  a  well 
dug  or  bored  to  and  through  the  porous  stratum  through 
which  it  flows.  Such  water  seldom  flows  in  the  form  of  a 
stream,  nor  is  it  collected  in  caverns  as  "  underground 
lakes";  but  generally  fills  the  porous  stratum  throughout, 
and  moves  slowly  through  the  interstices  towards  the  outlet. 


54  WATER-SUPPLY  ENGINEERING. 

This  movement  is  not  always  downward,  but  the  outlet  must 
always  be  lower  than  the  point  where  the  water  enters  the 
soil.  If,  in  travelling  through  such  stratum,  the  ground- 
water reaches  a  fault,  this  may  be  followed  to  the  surface 
and  the  water  emerge  as  one  or  more  springs. 

Art.  21.     Other  Sources. 

In  the  form  of  snow  and  ice,  water  is  stored  by  nature 
and  man.  Many  Swiss  streams  have  as  their  origin  thawing 
glaciers  formed  from  the  snowfall  of  many  years  ago.  Many 
thousands  of  tons  of  ice  are  stored  annually  by  man,  much 
of  which  is  used  in  and  for  drinking-water.  But  this  use  is 
only  incidental,  and  will  be  considered  only  in  reference  to 
its  purity. 

Dew  and  fog  have,  in  a  few  cases,  furnished  limited  sup- 
plies. Construction  camps  in  Mexico  have  found  supplies  of 
fresh  water  among  the  sand-dunes;  and  Laguna  Honda,  San 
Francisco,  among  the  sand-dunes,  gives  more  water  towards 
the  city  supply  than  the  rainfall  on  its  drainage  area  would 
furnish. 

Art.  22.     Relative  Use  of  Different  Sources. 

The  table  on  page  55,  compiled  from  the  "  Manual  of 
American  Water- works  "  for  1897,  shows  the  percentage,  in 
each  of  seven  divisions  in  the  United  States,  of  works  which 
utilize  each  of  the  several  sources  of  supply. 

The  indefiniteness  of  the  classification  used  by  the  differ- 
ent contributors  of  the  data  make  it  difificult  to  be  certain  as 
to  the  proper  placing  of  each  plant;  and  in  some  cases  two 
or  more  sources  are  used  by  the  same  city.  But  the  table 
gives  an  approximate  statement  of  some  interest  and  value. 
We  see  that  over  25^  of  the  plants  in  the  country  have 
ground-water  (well)  supplies,  the  largest  proportion  being  in 


SOU/iCES   OF  SUPPLY. 


55 


the  North-central  and  Northwest  sections;  and  that  New 
England  and  the  Middle  States,  with  their  hilly  country,  con- 
tain the  largest  number  of  surface  supplies.  Also  that  in  all 
the  Southern  States  rivers  are  used  more  generally  than  any 
other  one  source,  and  ground-water  next. 

Table  No.  14. 

percentage  of  cities  in  the  united  states  using  different 
sources  of  supply. 


New  England  . . 
Middle  States  . , 
South    Atlantic    and 

South-central 
North-central  .. 

North-west 

South  Pacific.  . . 

Pacific 

Whole  United  States 


Sur- 
face. 

Creek. 

Brook. 

River. 

Lake. 

Spring. 

Well. 

14.0 

16.3 

14.0 

27.1 

17-4 

7-7 

».3 

14.8 

10.7 

21.6 

4.4 

25-1 

14. 1 

3-1 

8.6 

4-7 

29.7 

4-7 

4-7 

21.9 

3-0 

4-5 

26.1 

13.2 

9.0 

41-5 

3.0 

6.0 

0.4 

26.6 

2.6 

4-7 

48.5 

4.8 

10.9 

1-4 

44.8 

1.4 

II. 5 

23.8 

3-0 

14-3 

6.0 

28.6 

3-0 

20.3 

21.8 

6.1 

8-3 

6.1 

25-4 

9.1 

16. 1 

25-7 

Un- 
known. 


3-5 
1.0 


In  the  next  few  chapters  the  sources  above  referred  to 
will  be  considered  at  length. 


CHAPTER   V. 
rainfall. 

Art.  23.     Quality  of  Rain-water. 

There  is  a  popular  impression  that  all  rain-water  is  as 
pure  as  any  natural  water  obtainable,  but  this  is  not  borne 
out  by  analyses.  In  fact,  it  is  not  reasonable  to  expect  to 
find  it  so  when  we  consider  the  large  amount  of  impurity 
contained  in  the  atmosphere,  and  recall  how  much  purer  and 
clearer  this  seems  after  a  rain.  This  impurity  consists  of 
dust  of  mineral  matters;  of  vegetable  pollen,  dried  particles 
of  insects,  and  other  organic  matter;  and  soot,  sulphuric 
acid,  ammonia,  carbon  dioxide,  and  other  acids  and  gases  are 
found  in  the  atmosphere  in  and  near  cities.  For  instance, 
Mabery  at  different  times  found  in  the  air  of  Cleveland,  O., 
the  following  quantities,  in  milligrams  per  liter  of  air: 


Soot. 

Sulphuric 

Acid. 

A 

mmonia. 

87.5 

15.2 

.070 

45.2 

6.3 

.010 

III. 3 

21.2 

.120 

41.8 

13-9 

.003 

Not  only  are  these  impurities  washed  from  the  air;  but, 
in  evaporation,  solid  matters  in  solution  are  carried  up  from 
water-surfaces.  Thus,  salt  from  the  ocean  is  found  in  rain; 
one  evidence  that  this  is  the  source  of  chlorine  in  rain-water 

56 


RAINFALL. 


57 


being  the  general  parallelism  of  isochlors  to  the  coast.  (See 
Plate  I,  page  15.) 

Bacteria  are  carried  down  in  small  quantities  by  rain,  but 
probably  none  of  these  are  pathogenic. 

The  following  analyses  are  given  by  the  Massachusetts 
State  Board  of  Health  in  their  Report  for  1890. 


Table  No.  15. 
analyses  of  rain-water. 


Collected  at 

Ammonia. 

Nitrogen  as 

Date. 

Free. 

Albu- 
minoid. 

Nitrates. 

Nitrites. 

Chlorine, 

July  7,  1888  .. 

Sept.  18,  18S8 

"     21,  18S8 

Oct.   2,    1888... 

Nov.  27.  1888 
May  21,  1889 
June  17,  1889 
Mar.  28,  1890 
Dec.  26,  1887 

North  Andover  . . 
Lawrence 

Jamaica  Plain.  . .  . 
Newton  Highlands 
Boston  (snow).  . .. 

*Troy,    N.  Y 

*Menands  Station, 
N.  Y 

.0047 
.0016 
.0298 
.0414 
.0164 
.0086 
.0564 
.0154 
.0258 
.0460 

.0150 

.0038 
.CO26 
.0024 
.0030 
.0014 
.0026 
.0152 
.0034 
.0038 
.0225 

.0060 

.0070 
.0040 
.0000 
.0100 
.0050 
.0030 
.0180 
.0050 
.0030 
.0200 

.0000 

.0000 
.0000 
.  OOOO 

.0000 
.0002 
.ooor 
.0004 
.0001 

.007 

.360 
.070 
.130 
.060 

.0000 
.0000 

.187 
.060 

*  From  Mason's  "  Sanitary  Water  Supply."     Both  snow. 

"  When  rain,  particularly  that  first  falling,  is  collected  in 
a  clean  glass  bottle,  it  is  seen  to  be  quite  dirty.  In  cities 
where  the  air  is  full  of  soot  this  is  very  marked,  but  even  in 
the  open  coimtry  the  floating  matter  in  the  atmosphere  is 
considerable.  At  the  close  of  a  protracted  rain  the  water 
may  be  nearly  or  quite  clear,  since  the  air  has  then  been 
washed  clean;  and  the  ammonia  is  also  less  than  at  the 
beginning  of  a  rainfall.  A  part  of  the  ammonia  in  the  rain- 
water has  its  origin  in  the  direct  formation  of  ammonia  from 
the  nitrogen  of  the  air  and  the  hydrogen  of  the  watery  vapor, 
but  its  main  source  is  undoubtedly  in  animal  exhalations,  fine 


58  WATER-SUPPLY  ENGINEERING, 

particles  of  organic  dust,  gaseous  products  of  decay,  etc." 
(Mass.  State  Board  of  Health,  Report  for  1890.) 

A  larger  proportion  of  the  snow  than  of  the  rainfall  is 
frequently  contributed  to  the  run-off,  but  the  total  amount 
in  any  but  extreme  northern  localities  is  not  considerable 
(snow  on  melting  reduces  to  about  one  tenth  its  bulk  of 
water),  although  sufficiently  so  to  be  of  some  importance. 
Snow  usually  removes  more  impurity  from  the  atmosphere 
than  does  rain,  owing  to  its  form.  This  greater  impurity  of 
snow  is  seen  in  the  above  table,  the  Troy  and  Boston  records 
being  city  snow;  the  Menands  Station,  country  snow. 

Rain-water,  on  account  of  its  softness,  is  especially 
adapted  to  washing;  and  where  the  public  supply  is  hard, 
roof-water  collected  in  cisterns  may  form  a  very  advantageous 
auxiliary  supply  for  this  purpose.  It  is  also  a  most  whole- 
some beverage  if  so  collected  and  stored  as  to  retain  its 
original  purity,  since  the  impurities  which  it  contains  are  not 
generally  injurious  unless  allowed  to  accumulate  and  putrefy. 
Unfortunately  the  method  of  collecting  and  storing  private 
supplies  is  often  very  faulty.  Every  roof  before  a  rain  is 
foul  with  excrement  of  birds,  dead  insects,  leaves,  and  dust, 
and  in  too  many  cases  all  of  this  is  washed  into  the  cistern. 
The  first  part  of  each  rain  should  be  run  to  waste,  and  only 
after  the  roof  is  washed  clean  should  the  water  enter  the 
cistern.  There  are  many  automatic  devices  for  accomplish- 
ing this,  but  few  are  in  common  use.  A  simple  two-way 
valve  in  a  tin  or  copper  breeches-pipe  at  the  bottom  of  the 
rain-water  leader,  to  be  turned  by  hand,  is  a  common  and 
efficient  contrivance,  if  properly  used  and  always  so  left  after 
a  storm  as  to  waste  the  water  until  turned. 

The  best  tank  for  storing  water  is  made  of  slate.  Iron 
properly  coated  to  prevent  rust  is  excellent  also.  Particularly 
in  the  South,  cypress  wood  is  much  used  for  cisterns. 
Masonry  walls  are  ordinarily  used  for  underground  cisterns, 


RAINFALL.  59 

but  should  be  absolutely  tight,  and  this  condition  should  be 
tested  at  intervals  of  not  more  than  one  year.  For  a  time, 
at  least,  water  stored  in  these  is  apt  to  be  hard  owing  to  the 
lime  in  the  mortar. 

Tanks  or  cisterns  should  always  be  covered  to  keep  out 
dust  and  other  impurities.  They  should  also  be  so  located 
and  so  tightly  constructed  that  contamination  from  outside  is 
absolutely  impossible.  If  underground,  their  bottoms  should 
be  above  the  top  of  the  sewage  in  any  cesspools  located 
within  a  radius  of  lOOO  feet;  and  if  privies  or  other  surface 
deposits  of  excreta  be  located  within  that  distance,  the  tank 
should  be  entirely  above  ground.  The  air  reaching  the  tank 
should  be  pure;  and  no  overflow  or  other  pipe  should  connect 
it  directly  with  the  sewer.  In  New  Orleans,  where  a  large 
part  of  the  water-supply  is  from  private  cisterns,  "  the  usual 
capacity  of  the  dwelling-house  cistern  is  about  two  thousand 
gallons.  They  are  raised  a  few  feet  from  the  ground,  and  their 
contents  are  protected  by  a  lid  or  cover.  Some  are  placed 
under  the  shade  of  a  balcony;  a  few  have  a  special  roof  over 
them;  but  the  majority  have  only  such  protection  from  the 
rays  of  the  sun  as  is  afforded  by  their  position  against  the 
house-wall.  Many,  especially  in  the  older  parts  of  the  city, 
are  situated  in  unventilated  inclosures  which  are  rank  with 
the  emanations  from  unclean  privies."  (Dr.  Smart,  Bulletin 
National  Board  of  Health,  April  17,  1880.)  The  deposit  in 
New  Orleans  cisterns  Dr.  Smart  found  to  collect  at  an 
average  rate  of  an  inch  a  year.  Sediment  collects  from  all 
rain-water,  and  should  be  removed  before  reaching  any  con- 
siderable amount,  since  it  is  stirred  up  by  the  inflow  from 
each  rain,  and  the  organic  matter  therein  is  continually 
decomposing. 

The  following  table  gives  the  analyses  of  a  few  cistern- 
waters  : 


6o 


WATER-SUPPLY  ENGINEERING. 

Table  No.   16. 

analyses  of  cistern-waters. 

(Nichols'  "Water-supply,  Chemical  and  Sanitary.") 


Total 
Solids. 

Ammonia. 

Chlorine. 

Locality. 

Free 

Albu- 
minoid. 

Authority. 

5.28 
6.56 

3-24 
4.80 
3.48 
5.20 
5.05 
6.90 
3.60 
2.68 
4.72 
4.48 
7.96 
4. 10 

0.013 
0.012 
0.005 
0.024 
0.021 
0.007 
0.002 
0.016 
0.005 
0.004 
0.275 
0.027 
0.004 
0.020 
0. 1050 

0.008 
0.007 
O.OII 
0.016 
0.007 
0.007 
0.015 
0.008 
0.008 
0.123 
0.055 
0.I18 
0.016 
0.360 
0.0175 

0.32 
0.36 
O.IO 
0.12 
0.69 
0.70 
0.70 
0.52 
0.52 

0.55 

2.76 

1.97 

trace 

trace 

0 . 2000 

W.  R.  Nichols 

.< 

<< 

<  ( 

Same    filtered  * 

<< 

Wilmington,    N.  C 

Cincinnati    O 

C.  W.  Dabney 
C.  R.  Stuntz 

.. 

" 

<• 

<« 

.. 

<< 

West  Troy    N    Y 

W.  P.  Mason 

*  These  cisterns  were  provided  with  a  brick  filtering-wall— the  inefficiency  of  which  is 

evident. 


Art.  24.     Quantity  of  Rainfall:  Annual. 

Rainfall,  being  the  origin  of  all  supplies,  is  the  basis  of 
calculation  of  the  amount  available  from  whatever  source, 
and  a  consideration  of  the  amount  of  rainfall  is  an  essential 
foundation  for  further  discussion. 

The  rain  which  will  fall  at  any  one  place  in  any  day, 
month,  or  year  cannot  be  accurately  predicted  by  any  known 
theory  or  science;  but  a  record  of  past  rainfalls  will  afford  an 
aid  to  our  judgment  in  estimating  such  amount,  and  in  fact 
forms  practically  the  only  basis  for  such  judgment;  although 
in  some  cases  probable  changes  in  certain  large  features  of 
the  country — such  as  deforestation — may  be  considered. 
(Authorities  differ  as  to  whether  the  presence  of  forests 
causes  increased   precipitation ;  but  there  seems  to  be  little 


RAINFALL. 


6i 


proof  that  such  increase,  if  it  is  so  effected,  is  at  all  consider- 
able in  amount.) 

Table  No.  17  gives  the  mean,  maximum,  and  minimum 
annual  precipitation  in  the  United  States  for  each  of  twenty- 
one  districts  into  which  the  Weather  Bureau  has  divided  the 
country;  and  Table  No.  18  the  same  also  arranged  according 
to  altitudes,  showing  the  maximum  and  minimum  averages 
for  all  places  in  each  district  within  the  indicated  range  of 
elevation.  For  instance,  of  all  stations  in  New  England 
having  an  altitude  of  less  than  lOO  feet  above  sea-level,  the 
maximum  average  precipitation  found  at  any  one  is  45.18 
inches,  and  the  minimum  40.73  inches.  These  tables  are 
based  on  all  records  up  to  Jan.   i,   1899. 


Table  No.  17. 
mean  annual  precipitation  in  the  united  states. 

(Mean,  Maximum,  and  Minimum  Averages  of  Stations 
in  each  Meteorological  District.) 


Mean 43.46    43.75 

Maximum 

Minimum 


47-5I     52-34 
35-74    37-89 


m 


54.09 
66.41 
47-55 


49.78 
57.98 
38.46 


54-25 
62.61 


43-15 
53-63 
29.70 


O  a; 
O 


45-45 
54-97 
36.68 


35-45 
41.28 

30-93 


32.61 
35 -cS 
29-53 


.8.95 

23-77 
14.70 


34.31 
42.83 
27^21 


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c 

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111 

c 

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A 

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go 

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i 

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2: 

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CO 

3°-25 

14-39 

22.33 

21.61 

8.44 

12.22 

16.36 

45-27 

29.81 

14-59 

39-93 

.5-77 

18.27 
12.20 

33  29 
12. II 

2-    02 

14.25 
2-97 

16.19 

8.48 

18.25 

'5-»5 

62.27 

35.16 

45-83 
20.87 

21.52 
9.00 

18.19 

62 


WATER-SUPPLY  ENGINEERING. 


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RAINFALL.  63 

The  total  annual  rainfall  is  seldom  the  same  for  any  two 
years  at  the  same  place,  or  at  any  two  places  for  the  sanie 
year;  and  its  variations  seem  to  follow  no  fixed  law.  During 
a  dry  season  at  one  place  another  scarcely  100  miles  away 
may  be  visited  by  a  wet  one.  Table  No.  21,  page  74,  illus- 
trates the  latter  statement  very  plainly.  For  instance,  in  the 
Eastern  Gulf  States  in  1898  the  precipitation  at  one  station 
was  15.61  inches  greater  than  the  average,  and  at  another 
12.97  inches  less,  the  average  precipitation  for  that  district 
being  54.25  inches,  or  less  than  twice  the  range  of  variation. 
Plate  IV  illustrates  the  variations  in  annual  rainfall,  as  just 
stated,  Philadelphia,  Vineland,  and  New  Brunswick  all  being 
within  a  radius  of  35  miles.  While  there  is  a  general  simi- 
larity in  the  curves,  the  variations  are  seen  to  be  numerous 
and  pronounced,  particularly  between  1875  and  1885. 

The  twenty-one  districts  into  which  the  Weather  Bureau 
has  divided  the  United  States  for  meteorological  purposes 
are  indicated  by  dotted  lines  on  the  map,  Plate  V,  while  the 
precipitation  averages  for  these  districts  are  tabulated  in 
Tables  No.  17  and  No.  18,  and  the  records  have  been  used 
for  other  tables  also.  A  comparison  of  the  district  records 
given  in  Table  No.  17  indicates  that  many  combinations  of 
districts  might  be  made,  as  far  as  precipitation  is  concerned, 
and  the  discussion  of  monthly  rainfall  in  the  next  paragraph 
shows  additional  reason  for  this.  The  author  has  found  it 
practicable,  by  comparing  curves  of  annual  and  more  particu- 
larly of  monthly  precipitation  in  the  various  districts,  to  so 
group  these  as  to  make  only  eight  divisions  of  the  country, 
as  shown  in  Plate  V  by  the  full  lines.  These  divisions  will 
be  hereafter  referred  to  as  "precipitation  districts,"  the 
smaller  ones  as  "  meteorological  districts." 

Although  in  each  meteorological  district  the  general  law 
and  average  amount  of  precipitation  are  practically  uniform, 
in  some  the  variation  between  the  precipitation  at  different 


64 


WA  TER-SUPPL  V  ENGINEERING. 


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PHILADELPHIA.         AVERAGE,  43.35 
VINELAND.                          "            48.39 
NEW  BRUNSWICIC.           "            46.91 

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RAINFALL. 


65 


66  WATER-SUPPLY  ENGINEERING. 

stations  is  as  great  as  the  variation  between  the  extreme  dis- 
trict means.  For  instance,  in  the  Southern  Plateau  the 
maximum  mean  (14.28  inches)  is  almost  five  times  the  mini- 
mum (2.97  inches);  and  in  Utah  alone  the  maximum  (18.45 
inches)  is  about  three  times  the  minimum  (6.28  inches). 
But  in  most  districts  the  extreme  variations  from  the  district 
average  is  from  10  to  40  per  cent. 

The  bounds  of  the  precipitation  districts  are  seen  to  be 
determined  to  a  large  extent  by  pronounced  natural  features 
— as  the  Pacific  Coast  Range,  the  Rocky  Mountains,  the 
Mississippi  and  its  western  tributaries,  its  eastern  tributaries, 
and  the  river-basins  of  the  Gulf  of  Mexico  and  South  Atlantic. 
The  factor  most  influential  in  determining  the  amount  of 
rainfall  in  a  given  district  is  its  position  relative  to  mountain 
ranges  and  to  the  sea  or  other  large  body  of  water.  Thus,  the 
warm,  moist  winds  of  the  North  Pacific  are  robbed  of  a  large 
part  of  their  moisture  by  the  west  slope  of  the  Sierra  Nevada 
and  Cascade  Range,  leaving  little  for  the  plateau  to  their 
east.  The  winds  blowing  over  the  Gulf  Stream  into  the 
South  Atlantic  and  Gulf  States  yield  their  moisture  to  them; 
and  as  they  ascend  the  valley  of  the  Mississippi  and  its  tribu- 
taries their  moisture  and  the  consequent  rainfall  decreases. 
Above  Cape  Hatteras  the  departure  of  the  Gulf  Stream  from 
the  coast  causes  its  influence  to  be  less  felt  in  precipitation, 
so  that  the  winds  from  the  Gulf,  after  passing  the  low 
countries  of  Louisiana,  Mississippi,  and  Alabama,  contribute 
more  rain  to  the  Ohio  valley  than  do  the  winds  from  the 
Atlantic  to  the  North  Atlantic  States. 

The  statement  has  been  made  that  precipitation  increases 
with  altitude  up  to  about  5000  feet,  above  which  it  decreases; 
but  this  is  true  for  certain  localities  only.  For  example,  San 
Francisco  for  a  number  of  years  had  as  a  minimum  annual 
precipitation  7.4  inches,  maximum  49.3  inches,  and  mean  23 
inches;  while  in  the  mountains  twenty-five  miles  distant  the 


Average  Annual 
Precipitation. 

19.80  in. 

23-33   " 

32-55   " 

44.01   " 

42.13  " 

50.77  " 

57-41   " 

47-93  " 

RAINFALL.  6"] 

minimum  precipitation  was  20  inches,  maximum  81  inches, 
and  mean  47  inches.  Also  the  following  rates  have  been 
found: 

Elevation. 

At  Sacramento,  Cal 30  ft. 

"   Folsom,  "   1S2  " 

"   Auburn,  "   1360  " 

"  Colfax,  "   2421   " 

"  Aha,  "   3612  " 

"  Emigrant  Camp,  Cal 5230  " 

"  Cisco,        Cal 5939  " 

"   Summit,     "    7017   " 

F.  H.  Newell,  Hydrographer  of  the  U.  S.  Geological 
Survey,  judges  from  data  obtained  that  on  the  western  slope 
of  the  Coast  Range  and  Sierra  Nevadas  "  there  is  a  regular 
increase  in  the  rate  of  precipitation  with  altitude,  and  that 
this  is  at  the  rate  of  0.6  in.  of  rain  for  each  100  feet  increase 
of  elevation."  S.  A.  Hill  has  shown  that  in  the  Northwest 
Himalayas  the  precipitation  may  be  represented  by  the 
formula 

I  -|-  1.92/^  —  0.40//'  +  0.02//', 

where  Ji  is  the  number  of  times  less  one  that  1000  is  con- 
tained in  the  elevation,  in  feet. 

Table  No.  18,  page  62,  shows  that  this  increase  of  pre- 
cipitation with  altitude  is  not  generally  true  all  over  the 
country.  Of  the  twenty-one  meteorological  districts,  in  but 
three  do  the  government  records  seem  to  show  that  this  law 
holds  uniformly  good,  viz.,  the  Upper  Lake,  Southern 
Plateau,  and  Southern  Pacific.  On  the  other  hand,  in  nine 
districts  the  opposite  seems  to  be  true,  and  the  precipitation 
decreases  with  the  altitude. 

It  has  also  been  stated  that  the  precipitation  decreases  in 
each  river-basin  with  the  distance  from  the  river's  mouth. 
This    is    true    of    the    Connecticut,    Hudson,    Susquehanna, 


68 


WATER-SUPPLY  ENGINEERING. 


Mississippi,  lower  Rio  Grande,  and  Columbia  rivers;  but  is 
not  true  of  the  upper  Rio  Grande,  Gila,  Rio  Colorado,  and 
others.  The  last-named  rivers  lie  in  the  Southern  Plateau 
and  Southern  Pacific  districts,  those  in  which  the  rainfall 
generally  increases  with  the  altitude.  The  two  statements 
are  apparently  one — as  we  rise  above  the  sea-level  and  recede 
from  the  coast  the  precipitation  becomes  less,  except  in  the 
southwest  and  possibly  along  the  Great  Lakes. 

The  general  statement  may  also  be  made  that  the  greatest 
precipitation  is  contributed  by  winds  from  the  Japan  Current 
in  the  northwest,  and  from  the  Gulf  Stream  in  the  southeast. 

The  problem  of  water-supply  is  concerned  rather  with 
minimum  than  with  maximum  rainfall,  and  the  system  must 
be  so  designed  that  there  shall  be  no  lack  during  the  longest 
periods  of  drought.  Reference  to  Plate  IV,  page  64,  shows 
that  the  minimum  rates  do  not  continue  for  more  than  one 
year,  although  at  times  loiv  rates  continue  for  three  to  five 
consecutive  years.  These  cycles  of  lowest  rates  must  be 
provided  for  according  to  the  engineer's  best  judgment. 
When  long-period  rain-gaugings  are  available  they  should  be 
used  with  judgment;  but  even  those  extending  over  a  short 
period  are  useful  in  estimating. 

Table  No.  19  shows  the  percentages  of  the  average  annual 
precipitation  which  represent  the  minimum  average  for  any 
two,  three,  four,  and  five  consecutive  years  in  three  cities. 

Table  No.  19. 

DRY    CYCLES    OF    FROM    TWO    TO    FIVE    YEARS'    DURATION. 


City. 

Length 

ot 
Record. 

Mean 
Precipita- 
tion. 

Dryest 
Year. 

Dryest 
3  Years. 

Dryest 
3  Years. 

Dryest 
4  Years. 

Dryest 
5  Years. 

Boston 

Philadelphia. 
Denver 

74  years 
68       " 
19       " 

47.00  in. 

43-35   " 
14.30  " 

58^ 
68!? 
65^ 

68^ 

11% 

11% 

76i^ 

78^ 
9,0% 

1C)\% 

19\% 

RAINFALL. 


69 


There  is  seen  to  be  a  close  agreement  between  the  Boston 
and  Philadelphia  cycles,  and  both  of  these  are  for  much 
longer  periods  than  the  Denver  ones.  It  is  of  course 
probable  that  the  longer  record  will  include  a  dryer  season 
than  the  shorter  one.  If  we  take  only  the  same  nineteen 
years  of  Boston's  and  Philadelphia's  rainfall  covered  by  the 
Denver  record  we  obtain  the  following  percentages: 


City. 

Length 

of 
Record. 

Mean 
Precipita- 
tion. 

Dryest 
Year. 

Dryest 
2  Years. 

Dryest 
3  Years. 

Dryest 
4  Years. 

Dryest 
S  Years. 

Boston 

Philadelphia. 

19  years 
19      " 

49.42  in. 
42.40    " 

12% 

85^ 
75i^ 

89*^ 
79^ 

87^ 
79$!^ 

88^ 
8ii^ 

In  each  case  the  nineteen  years  does  not  include  so  dry  a 
period  as  did  the  seventy-four  and  sixty-eight  years  respec- 
tively; an  illustration  of  the  fact  that  allowance  should  be 
made,  when  only  short  records  are  available,  for  dryer  periods 
than  those  recorded.  It  is  also  evident  that  the  percentages 
in  one  district  cannot  be  applied  to  another.  Thus,  Denver's 
dry-cycle  percentages  are  lower  than  those  of  either  Boston's 
or  Philadelphia's  for  the  same  period,  except  for  the  five-year 
cycle. 

The  greater  the  number  of  years  over  which  a  precipita- 
tion record  extends  the  closer  will  the  mean  obtained  be  to 
the  true  mean.  As  an  illustration,  the  mean  precipitation  at 
Philadelphia  for  15  years,  beginning  with  1825,  was  40.32 
inches;  for  30  years  it  was  42.45  inches;  for  45  years,  43.80 
inches;  for  60  years,  43.18  inches;  and  for  68  years,  43.35 
inches.  Hence  any  mean  precipitation  obtained  for  any 
place  will  only  approximate  the  true  mean;  more  closely, 
however,  the  longer  the  period  over  which  the  record  extends. 
In  certain  small  sections  of  the  country  one  or  even  two 
years  may  pass  without  any  rain  whatever  falling. 


"JO  WATER-SUPPLY  ENGINEERING. 


Art.  25.     Quantity  of  Rainfall:  Monthly. 

For  many  purposes  it  is  desirable  to  know  the  monthly 
precipitation  as  well  as  the  annual;  and  in  this  a  general  law 
is  in  most  cases  observable,  although  the  law  differs  in  differ- 
ent localities.  Table  No.  20  shows  the  mean  precipitation 
for  each  month  in  each  of  the  meteorological  districts;  and 
Table  No.  2  i  shows  the  monthly  variations  in  each  of  these 
districts.  The  former  gives  the  average  precipitation  of  all 
stations  for  each  month  and  for  the  year,  and  also  the  maxi- 
mum average  and  minimum  average  found  for  any  single 
station  in  each  district.  The  maximum  and  minimum  pre- 
cipitation for  any  one  month  or  year  would  be  considerably 
greater  and  less,  respectively,  than  these  figures.  In  Table 
No.  21  are  given  the  monthly  variations  in  each  of  the 
meteorological  districts  for  the  year  1898,  which  was  believed 
to  be  a  fair  average  year  as  regards  rainfall.  This  table 
shows,  for  each  district,  the  maximum  variation  by  which  the 
monthly  precipitation  at  any  one  station  was  greater  or  less 
than  the  average  precipitation  at  tJiat  station  for  that  month 
of  the  year.  -\-  signifies  that  the  precipitation  was  greater 
than  the  average;  —  that  it  was  less.  Where  the  precipita- 
tion at  all  stations  in  any  one  district  varied  on  the  same  side 
of  their  averages,  the  maximum  and  minimum  variations  are 
given.  This  table  illustrates  the  impossibility  of  accurately 
predicting  the  precipitation  for  any  month,  and  the  error  in- 
volved in  assuming  that  all  places  in  the  same  district  are 
subject  to  equal  variations;  since  more  than  ']']<fo  of  the 
monthly  records  show  variations  in  different  directions  in  the 
same  district. 

There  is,  however,  a  general  law  for  each  district  which  is 
subject  to  only  occasional  exceptions.  Thus,  in  New  England 
June  and  September  are  the  months  of  least  precipitation; 


RAINFALL.  7 1 

not  only  as  regards  the  district  mean,  but  the  maximum  local 
means  are  less  for  these  than  for  other  months,  as  are  also 
the  +  variations  in  Table  No.  21.  A  comparison  of  these 
laws  for  the  various  districts  shows  great  similarity  among 
certain  groups,  and  these  groups  have  been  made  the  basis 
of  the  subdivision  into  precipitation  districts  already  referred 
to.     These  districts  are  (see  Plate  V,  page  65): 

1.  The  North  Atlantic,  Ohio,  and  West  Gulf. 

2.  South  Atlantic  and  Gulf. 

3.  Upper  Mississippi  and  Great  Lakes. 

4.  Eastern  Slope. 

5.  Northern  and  Middle  Plateau. 

6.  Southern  Plateau. 

7.  North  Pacific. 

8.  Middle  Pacific. 

The  mean  rainfall,  monthly  and  annual,  for  these  districts 
is  shown  in  Table  No.  22,  page  ^6,  with  the  greatest  per- 
centage by  which  any  one  local  average  varies  from  the  dis- 
trict average. 

Except  in  the  case  of  the  fourth  district  the  variations  in 
these  Precipitation  Districts  are  little  greater  than  those  in 
the  Meteorological  Districts,  and  the  reduction  in  number 
makes  reference  more  easy.  This  division  is  also  in  accord 
wiih  the  more  important  laws  of  precipitation. 

In  Table  No.  23,  page  'j'j,  is  shown  the  mean  monthly  pre- 
cipitation for  four  cities,  together  with  the  maximum  and 
minimum  recorded  for  each  month. 

It  will  be  seen  from  this  table  that  at  Philadelphia  and 
Boston  the  rainfall  has,  during  each  month  in  some  year, 
been  less  than  i  inch ;  at  Charleston,  although  the  average 
annual  rainfall  is  less  than  at  these  two  places,  the  minimum 
monthly  precipitation  is  greater  for  every  month  but  one; 
while  at  Denver  the  minimum  monthly  precipitation  is  but 
2\  to  22f  per  cent  of  the  average  for  the  same  month. 


72 


WATER-SUPPLY  ENGINEERING. 


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76 


WATER-SUPPLY  ENGINEERING, 
Table  No.  22. 


MEAN    MONTHLY    PRECIPITATION,    BY    PRECIPITATION    DISTRICTS, 
AND    PERCENTAGES    OF    MAXIMUM    RANGE    OF    VARIATION. 


Jan. 

Feb. 

Mar. 

April. 

May. 

June. 

July. 

P 

d 

.2 

.2 

> 

c 
0 

.2 

c 

0 

'C 
> 

c 
> 

Pi 

c 

0 

rt 
> 

d 

.0 

.5 

u 
> 

a. 

d 
.S 

'u 
> 

I 

2 

3 
4 
S 
6 
7 
8 

3 
4 
I 
o 

2 
O 

8 
5 

9 
3 
9 
8 
o 
5 
I 
5 

69 

51 
100 

20 

57 
S3 

3-7 
3.8 
2.0 
0.7 
1.5 
0.8 
6.0 
4.1 

51 
56 
95 
171 
40 
50 
50 
49 

3 
4 
2 

I 
I 
0 
5 
4 

9 
6 
2 

4 
6 
5 
4 
0 

59 
74 
73 
64 
50 
40 
68 
62 

3.6 

3.0 

2-7 

1.8 
1.4 
0.3 
4-3 
2.4 

55 
93 
70 
61 
57 
167 

^5 

3-8 
4.0 
3-9 
2.8 
1.4 
0.4 
2.7 
1.6 

52 
47 
56 
89 

100* 
70 
88 

3-7 
5-5 
4.1 
3.0 

I.O 

0.3 

2-3 

°-5 

41 

38 

39 

73 

80 
200* 

77 
160 

3 

6 

3 

2 
0 
I 
0 
0 

8 
2 
5 
3 
4 
2 
8 
I 

66 
58 
49 
70 
75 

138 
50 

200 

Au 

%■         \ 

Sept. 

Oct. 

Nov. 

Dec. 

Year. 

u 

d 

d 

d 

d 

d 

«-*^ 

0 

0 

0 

2 

0 

x^ 

• 

rt 

rt 

01 

a 

u 

rt 

V 

« 

V 

.«z 

m 

rt 

rt 

rt 

rt 

rt 

!Tl 

rt 

0 

A 

> 

tf 

> 

a; 

> 

05 

> 

05 

> 

05 

> 

I 

4.0 

52 

3-5 

77 

3. 1 

51 

3-7 

49 

3-4 

62 

44.0 

—  32 

2 

6.4 

47 

5-4 

80 

3-9 

136 

3-3 

5« 

3-5 

54 

53-4 

—  28 

3 

3-1 

45 

3.0 

67 

2.6 

73 

2-3 

"3 

2.0 

75 

33-'^ 

-  52 

4 

2.0 

80 

1-5 

93 

1-3 

77 

0.7 

171 

0.7 

243 

18.6-} 

-  35 
+  79 

s 

0.3 

166 

1.0 

100 

I.I 

63 

1.2 

92 

1.9 

32 

14.6 

-  42 

6 

1.2 

83 

0.0 

100* 

0.6 

67 

0.5 

60 

1 .0 

100 

8.4 

-65 

7 

1 .0 

87 

3.2 

128 

5-3 

92 

7-5 

99 

8.9 

84 

45.3] 

—  22 

+  38 

8 

0.0 

0.7 

86 

1-7 

47 

3-0 

33 

5-6 

46 

29. 8J 

-38 

-f  54 

*  Never  any  rain  during  these  months  in  certain  localities. 

When  several  months  of  low  precipitation  follow  each 
Other  consecutively,  this  fact  will  have  considerable  bearing 
upon  the  question  of  storage.  In  none  of  the  records  from 
which  the  above  were  taken  did  two  months  of  minimum 
precipitation  follow  each  other;  in  many  cases  such  months 
were  immediately  preceded  and  followed  by  months  of  heavy 
rainfall;  and  in  the  majority  of  cases  the  average  of  any 
three  consecutive  months  including  the  minimum  was  at  least 
two-thirds  of  the  monthly  average  for  that  year.  There  are 
in  the  Boston  record,  however,  several  instances  where  the 
average   of  six   consecutive  months,   and   in   the   Charleston 


RAINFALL. 


77 


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78 


fVA  TER-SUPPL  V  ENGINEERING. 


record  several  where  the  average  of  four  consecutive  months, 
is  less  than  one-twelfth  the  minimum  annual  rainfall;  while 
in  Denver  there  are,  each  year,  six  months  of  light  and  six 
of  heavy  rainfall.  In  Massachusetts  the  mean  precipitation 
is  almost  exactly  the  same — 11.75  inches — for  each  of  the 
four  seasons,  spring,  summer,  autumn,  and  winter.  These 
three  records  fairly  well  represent  three  sections  of  the 
country. 

Table  No.  24  (from  Vermeule's  "  Report  on  Water- 
supply,  Geological  Survey  of  New  Jersey")  shows  the 
monthly  rainfall  during  two  typical  dry  periods  in  New  York 
and  Philadelphia;  while  Table  No.  25  shows  the  four  dryest 
periods  of  from  three  to  twelve  months'  duration  each,  in 
the  same  cities. 


Table  No.  24. 

TYPICAL    DRY    PERIODS. 
PHILADELPHIA    RECORD. 


Dec. 

Jan. 

..36 
1.44 

Feb. 

Mar. 

Apr. 

May. 

June. 

July. 

Aug. 

Sept. 

Oct. 

Nov. 

Year. 

1841- 

1842- 

1842 
1843 

S-92 
3-66 

4.27 
2.54 

2.84 
4-42 

5-31 
4.72 

5.87 
2.05 

3-19 
1.69 

II. 81 

4-54 

3-79 
9.36 

1.27 
4.86 

1.72 
3.22 

3-49 
4.18 

50.84 
46.58 

I879-I880 
I880-I88I 

4.69 
4-05 

3.66 

2.43 

4.76 

3" 
3-83 

2-43 
0.61 

0.54 
2.71 

1.67 
387 

7-74 
0.96 

5.09 
1. 18 

1. 10 
0.94 

1.74 
3.04 

'•75 
2.02 

.34-22 
3"  63 

NEW 

YORK    RECORD. 

I84I- 
1842- 

1842 

1843 

2.70 
3-5° 

1.07 
1 .00 

2.85 
2.31 

1.25 
2.13 

3.60 
2.14 

3.60 
1 .00 

3.30 
0.76 

3.80 
..64 

2.81 
15.26 

3.10 
3.C6 

430 
S.91 

1.80 
2.82 

33 -iS 
41-53 

1879- 

1880- 

1880 
I88I 

4.94 
a. 27 

2.02 
4.80 

2. 12 
4.93 

4.66 
5-8. 

2.90 
0-95 

0.62 
3.20 

1. 14 
5-35 

8.53 
1.25 

5.26 
0.86 

1. 8s 
0.97 

2.81 
1.60 

2.46 
2.36 

39-31 
34-35 

For  large  areas  and  where  storage-reservoirs  are  used,  the 
monthly  and  annual  precipitation  serve  all  purposes,  except 
the  calculation  of  storm  overflow  to  be  allowed  for;  but  for 
this  purpose,  and  for  the  immediate  collection  of  rainfall  in 
cisterns  and  on  small  watersheds,  it  is  desirable  to  know  the 
maximum   rates   of  precipitation   for  short    periods.      Table 


RAINFALL. 

Table  No.  25. 

dry  periods.     new  york  and  philadelphia  rainfall. 


79 


New  York. . 

Philadelphia 
New  York  . . . 

Philadelphia 
New  York. . . 

Philadelphia 
New  York.. 
Philadelphia 
New  York. . . 
Philadelphia 

New  York  . . . 

Philadelphia 
New  York  .  . 
Philadelphia 
New  York. . . 
Philadelphia, 
New  York . . 

Philadelphia 
New  York . . 
Philadelphia 
New  York. . . 

Philadelphia 
New  York. . , 

Philadelphia 
New  York.  . , 
Philadelphia 
New  York. . . 


Date. 


Aug.  iS42-July  1843 
Jan. -Dec.  1836 
"     1825 
"         "     1840 
Sept.  1842-July  1S43 
Jan. -Nov.  1836 
"      1825 
Feb. -Dec.  1840 
Oct.  1842-July  1S43 
March-Dec.  1881 
Jan. -Oct.  1836 
"     1825 
Nov.  1842-July  1843 

April-Dec.  1881 
Oct.  i87g-June  1880 

Jan. -Sept.  1849 

Dec.  1842-July  1843 

April-Nov.  1881 

Oct.  1879-May  1880 
Jan. -July  1843 
April-Oct.  1881 
Jan. -July  1849 
April-Oct.  1881 
Feb.-Julv  1843 

April-Sept.  18S1 
July-Dec.  1881 
Jan. -July  1880 
July-Nov.  1881 

March-July  1843 
Jan.-Mav  1836 
July-Nov.  1881 
July-Oct.  1881 
April-July  1843 
July-Nov.  1881 
April-July  1849 
July-Sept.  1881 

May-July  1843 
Jan. -March  1836 


Duration, 
Months. 


12 
12 
12 
12 
II 
II 
II 
II 
10 
IQ 
ID 
10 
9 
9 

9 
9 
8 
8 
8 
8 
7 
7 
7 
7 
6 
6 
6 
6 
5 
5 
5 
5 
4 
4 
4 
4 
3 
3 
3 
3 


Total 
Rainfall. 


25.48 
27-57 
29-57 
29.80 
22.67 
25.27 
25-85 
27.96 

20.57 
21-79 
23-37 
24-49 
16.27 
17.96 
18.59 
20.22 
14.47 
15-32 
16.54 
16.92 
11.97 
13.30 
14.04 
14.18 

9-97 

10.26 

11.22 

12.  II 

7.04 

7.67 

7.70 

8.14 

4.68 

5-54 
6. 12 
6.30 
3.08 
3.08 
3-40 
4.41 


Rainfall 

per 
Month. 


2.12 
2.30 
2.46 
2.48 
2.06 
2.30 

2-35 
2-54 
2.06 
2.18 
2-34 
2-45 
1. 81 
1.99 
2.07 
2.25 
1. 81 
1. 91 

07 
II 

71 
90 
01 

03 
1.66 
1. 71 
87 
02 

41 

53 
54 
63 
17 
1-39 
1-53 
1.58 
1.03 
1.03 

I-I3 
1.47 


No.  26  gives  the  maximum  recorded  rates  in  various  locali- 
ties, which  will  probably  be  exceeded  only  at  long  intervals, 
if  at  all. 


Bo 


WA  TER-SUPPL  V  ENGINEERING. 


Table  No.   26. 
maximum  amounts  of  rain  falling  during  different  periods 

OF    TIME. 


Length  of  Period  in  Minutes. 

to 

15 

25 

30 

4S 

60 

Over  60. 

Place  and  Date. 

5 

Amt. 

Dura- 
tion. 

0.50 

S.ao 

24  h. 

Boston,  Oct.  12,  1895 

.1         >■  1879-1891 

"        July  18,  1884 
Providence,  R.  I.,  May  i8,  1877 
"       Aug.  29,  1877 
6,  1878 

1.40 

0.80 
0.70 

::;; 

1.50 
1.30 

0.50 
1.50 

... 

2.56 

0.90 

0.75 

1.74. 

5-03 
1.18 

uh. 
2h. 

Ithaca,  N.  Y.,  Aug.  4,  1892.     Preceded  by 

5  hours  of  light  rain 
Mt.  Carmel,  N.  Y.,  July  2,  1897 
Morrisania,  Oct.  30,  1866 
New  York  City,  Sept.  19,  1894 
';        "        "      Aug.  19,  1893 

7  times  during  1869-1891 

"       3 

"        '         '        5     "            "          "       " 

May  4,  1893 
"        "        "                    1882             [sewer) 
"        "        "       July   6,    1896.    (Gorged   a 
Brooklyn,  N.  Y. 
Spring  Mount,  Pa.,  June  6,  1893 

■■     during  i8q3  (4  storms) 
Philadelphia,  Pa.,  2  times  during  1884-1891 

i               '..'      3      "!          ii           !1      !'i 
"               "      March,  1890 
Baltimore,  1896 

0.50 

0.35 

1.40 

1.20 

0.80 

0.60 

1.30 

1.50 

* 

3.60 
6.17 

24  h. 
24  h. 

0.80 

1.00 

1. 00 
1. 00 
1. 00 
0.80 
0.60 

0.40 

0.35 

0.60 

1.60 
0.80 
0.60 

0.85 

0.70 

0.75 

1.20 
0.60 

2.60 

0.25 

1^28 
.... 

1.50 
1.60 
1.30 

0.45 

" 

1. 00 
0.96 
0.64 

0.21 
0.25 
0.80 

0.46  0. 58 
0.81; >■-"•' 

0.6;' 

0.95 

0.83 

0.9s 

1.30 

2.00 
1.50 

Washington,  D.  C,  2  times  during  1871-1891 
''       5     "             ' 

0.52 
o.so 
0.40 

0.75 
1.20 
1. 00 
1.20 
1.50 
1. 00 

1:48 
1.32 
1.82 
'■75 
1. 17 

I  lei 
1.95 
2.00 
'•25 

2.05 

1.87 

2.10 

2.00 
2.70 
2.62 
2.45 
2.20 

3-40 
3-19 
2.70 
2.32 

6.00 
3-3° 

2  h.' 
2h. 

"                 "     mean  of  many  rains 
New  Orleans,  June  17,  1895 

"                "           Alio-     lo-  tRqj 

0.60 
0.2s 

2-35 

lih. 

July  4,       " 

"  14.      " 
'        Sept.,  1889  (2  storms) 

4.12 
1.78 

1. 71 
1. 15 
1.50 
0.88 
1. 10 

3.60 
1.63 

1.99 
1.80 

1. 00 
1.23 

0-35 

0.65 
0.20 

0.61 
0.26 
0.30 

0-45 
1. 00 
0.80 
0.60 

0.90 

0.47 
0.70 
0.44 

0-37 
0.57 

1. 15 

0.85 
0.92 
0.77 
0.47 
0.65 

1.40 

0.90 
1.30 
0.82 
0.62 
0.77 

1-55 

I  01 

1-57 
0.91 
0.75 
o.go 

Anril  ia.  I'ini.    Preceded    bv 

6  hours  of  light  rain 

0.30 
0.07 

(Jacksonville,  Fla.,  U.  S.  Weather  Bureau, 
1      1896 

1  Galveston,  Texas,  1896.      U.  S.  Weather 
)      Bureau 
Chicago,  once  during  1889-1S91 

0.30 

"        2  times     "        "        " 

1 .10 

1-75 
3-3>^ 

2h. 
2h. 

Ohio  Valley,  July  16,  1896 

St.  Louis,  May  14,  1891 

0.28 
0.04 
o.is 
0.38 
0.25 
0.06 
0.35 

0  58 
o.lq 
0.45 

0-57 
0.50 
0.33 

0.88 
0.49 

1.13 
0.79 

1-23 

1.04 

1.07 

•••3 

0.99 
0.66 

1.38 
1. 31 
1. 14 
1.30 
1.02 
0.70 

Cleveland,  Ohio,  18^6  "1 

Detroit,  Mich.,         "      1  U.  S.  Weather 

'•73 

o.63'o.9i 

1.70 

1.78 

"           "              "      [      Bureau 
Little  Rock,  Ark.,  " 

0.46 

0.60 

0.79 

0.91 
0.82 
II. 5+ 
8.8 

J 

San  Diego,  Cal.,  December,  1896 
Campo,  Cal.,  August,  1891 

ix 

■2VhV 

2  h. 

Palmetto,  Nev.,     "       1890 
!•  Island  of  St.  Kitts 

RAINFALL. 


8i 


Art.  26.     Gauging  Rainfall. 

Measurements  of  snow  are  ordinarily  recorded  in  inches 
of  fall  as  found  upon  a  level  surface  free  from  drifts;  but  it 
is  very  difficult  to  obtain  an  average  depth  in  windy  weather, 
although  the  best  judgment  must  be  used  to  ascertain  this. 
Generally,  besides  expressing  this  in  inches,  a  cylinder  of 
snow  of  this  depth  is  collected  and  melted  in  a  can  or  tube 
of  the  same  diameter  as  the  cylinder  of  snow,  and  the  depth 
of  water  resulting  is  recorded  as  precipitation  or  rainfall. 

Measurements  of  rainfall  are  taken  by  rain-gauges;  the 
most  common  form  consisting  of  a  circular  cup  of  thick  brass, 
its  top  brought  to  a  chisel-edge,  the  bottom  cone-shaped  and 
connected  with  a  deep  tube  of  known 
diameter  into  which  the  rain  flows 
from  the  cup.  (See  Fig.  2.)  The 
area  of  the  top  of  the  cup  and  that 
of  the  tube  bear  a  known  relation  to 
each  other, — 10  to  i  is  a  convenient 
ratio, — and  the  depth  in  the  tube  is 
measured  by  a  stick  so  graduated 
that,  when  it  is  lowered  to  the  bottom 
of  the  tube,  the  scale  will  give  the 
actual  depth  of  rainfall,  allowance  being  made  in  the  scale  for 
both  the  relative  areas  and  the  displacement  of  the  stick. 
The  depth  is  customarily  expressed  in  inches  and  decimals 
of  an  inch.  The  readings  are  taken  daily  and  at  the  begin- 
ning and  ending  of  each  storm. 

For  many  purposes  it  is  desirable  to  know  the  rate  of  fall 
for  short  intervals  of  five  minutes  or  less,  and  for  ascertaining 
this  self-recording  gauges  are  necessary.  Several  styles  of 
such  gauge  have  been  used.  One  is  the  "  tipping-tank, " 
which  tips  and  empties  itself  as  soon  as  it  has  received  .01 
inch  of  rainfall,  immediately  returning  to  an  upright  position, 


Fig.  2. — Rain-gauge. 


82  WATER-SUPPLY  ENGINEERING. 

the  time  of  each  discharge  being  automatically  recorded. 
Another  gauge  consists  of  a  tank  suspended  by  a  spring- 
balance,  a  pencil  attached  to  the  tank  continuously  recording 
its  vertical  position  upon  a  cylinder  revolved  by  clockwork 
once  in  twenty-four  hours.  In  using  any  recording-gauge 
the  total  water  caught  should  be  retained,  and  measured  or 
weighed  each  day  as  a  check  upo'n  the  record. 

The  size  of  the  collector-cup  seems  to  have  some  effect 
upon  the  catchment.  For  example,  of  four  3-inch  cups  and 
one  8-inch  one,  in  use  on  Mt.  Washington,  the  average  total 
amount  collected  by  the  3-inch  cups  in  one  year  was  46.26 
inches,  while  that  recorded  by  the  8-inch  cup  was  58.70 
inches.  It  is  probable  that  the  larger  the  collector-cup  the 
more  accurate  the  result.  The  position  of  the  gauge  relative 
to  the  ground-surface  also  influences  the  amount  of  catch- 
ment, those  placed  near  the  surface  generally  giving  the 
larger  results.  It  has  been  found  that  a  gauge  lOO  feet 
above  the  ground  will  give  on  an  average  but  65^  as  much  as 
one  on  the  surface.  Experiments  seem  to  show  that  the 
intensity  of  the  wind  is  the  controlling  factor  in  these  varia- 
tions. (See  the  Weather  Review  for  June,  1897.)  It  is 
maintained  by  many  that  gauges  at  the  surface  give  less 
accurate  results,  since  they  receive  not  only  the  actual  pre- 
cipitation, but  also  a  certain  amount  of  moisture  from  the 
surrounding  ground  which,  after  falling,  again  rises  by 
splashing  and  evaporation  and  is  reprecipitated.  A  large 
number  of  the  gauges  of  the  signal  service  are  placed 
upon  the  roofs  of  tall  buildings,  and  in  cities  this  is  generally 
necessary;  but  in  open  country  a  height  of  3  to  6  feet 
from  the  surface  will  probably  give  the  most  accurate  results. 
The  gauge  should  be  at  least  as  far  from  any  building 
or  other  obstacle  as  the  top  of  this  is  above  the  gauge. 
The  rim  of  the  collector-cup  should  be  level. 

The   U.    S.   Weather  Bureau  has  for  years   been  taking 


RAINFALL.  "         83 

records  of  precipitation  in  various  parts  of  the  country,  and 
about  150  stations  are  now  operated  by  them;  records  being 
received  from  hundreds  of  voluntary  observers  also.  These 
records  are  available  to  any  one,  and  should  be  consulted  in 
the  study  of  the  precipitation  at  any  locality. 

Art.  27.     Storage  of  Rain-water. 

Since  rainfall  is  not  only  not  continuous,  but  droughts  of 
considerable  duration  may  be  expected  any  year,  users  of 
rain-water  must  arrange  to  store  a  sufficient  amount  to  carry 
them  over  the  dry  seasons.  A  dwelling  25  by  40  feet, 
having  a  roof  of  1000  square  feet  area,  would,  if  in  Phila- 
delphia,   receive     upon     this     roof    an    average    amount     of 

(1000  X  — '- — j,   or  3613.5   cubic  feet  per  year,   or  74  gals. 

per  day.  But  43.35  inches  is  the  mean  of  68  years,  and  for 
five  successive  years  an  average  of  but  79^^  of  this  amount 
fell;  for  three  years  ']'j\io,  for -two  years  but  Tl^i^,  and  for 
one  year  but  68^  of  this  amount  was  precipitated.  (Table 
No.  19,  page  68.)  Moreover  we  see  by  Table  No.  23,  page 
J'j,  that  a  monthly  rate  of  0.19  inch  has  occurred  in  March, 
and  we  judge  from  Table  No.  25  that  for  six  months  the  rate 
may  be  only  1.71  inch  per  month.  It  is  thus  apparent  that 
if  we  need  a  continuous  supply  of  only  about  35  gals.,  suffi- 
cient storage  to  make  up  the  occasional  deficiency  during  only 
the  six  dryest  months  is  required;  if  about  50  gals,  per  day 
is  needed,  storage  for  one  dry  year  is  required;  while  if  57 
gals,  is  needed,  storage  must  be  provided  to  tide  over  three 
dry  years. 

What  the  amount  of  storage  must  be  may  be  determined 
by  a  calculation  similar  to  that  shown  on  the  next  page. 
Taking  the  year  from  December,  1879,  to  November,  1880, 
inclusive   (see   Table   No.  24,  page   78),  we   find  the  average 


84 


WATER-SUPPLY  ENGINEERING. 


precipitation  for  this  year  in  Philadelphia  was  34.22  inches, 
or  an  average  monthly  rate  of  2.85  inches.  If  we  assume 
the  cistern  as  empty  at  the  beginning  of  this  period  we  will 
have  the  following  condition  from  month  to  month. 


Month. 


Amount 
in  Reser- 
voir at 
First  of 
Month. 


Amount 
of  Pre- 
cipitation, 
cu.  ft.  per 
Month. 


Con- 
sumption. 
2.85  in.  or 
237.64  cu 
ft.  per. 
Month. 


Surplus 
Added  to 
Reservoir 


Deficiency 
to  be  Sup- 
plied by 
Reservoir 


Amount 
in  Reser- 
voir at 
End  of 
Month. 


December 
January. . . 
February.. 
March. .  . 

April 

May 

June 

July 

August.  .  . 
September 
October. . . 
November. 


Cu.  Ft. 
0.000 

153-19 

41.38 

6.24 

62.77 

27.63 

—  165.01 

—  263.48 
143-88 
330-40 
184.43 

91.79 


Cu.  Ft. 

390  83 
125.83 
202. 50 
294.17 
202. 50 
45.00 

139-17 
645 . 00 
424. 16 
91.67 
145.00 
145-85 


Cu. 
237 
237 
237 
237 

237 
237 
237 
237 
237 
237 
237 
237 


Ft. 
.64 
.64 
.64 
.64 
.64 
.64 
.64 
.64 
.64 
.64 
.64 
.64 


Cu.  Ft. 
15319 


Cu.  Ft. 


56-53 


III. 81 
35-14 


407.36 
186.52 


35-14 

192.64 

98.47 


145-97 
92.64 
91.79 


Cu.  Ft. 

153-19 

41.38 

6.24 

62.77 

27.63 

—  165.01 

-263.48 

143-88 

330-40 
184.43 

91.79 
0.00 


It  appears  from  this  that  there  should  have  been  in  the 
cistern  on  December  1st  at  least  263.5  cubic  feet  of  water  to 
make  up  the  deficiency  during  January  to  June,  inclusive; 
the  cistern  would  then  have  been  empty  on  July  1st,  but 
during  July  and  August  would  have  received  about  600  cubic 
feet  surplus  and,  if  sufficiently  large  to  hold  this  amount, 
would  on  December  ist  again  contain  263.5  cubic  feet  to  pro- 
vide for  the  following  year.  But  this  is  on  the  assumption 
that  all  the  rainfall  is  collected.  Even  in  a  dry  year,  how- 
ever, unless  the  water  is  carefully  filtered,  the  first  of  each 
rain  should  be  wasted,  and  this  will  probably  require  at  least 
\  inch  each  month.  Making  this  allowance  we  find  that 
410.5  cubic  feet  must  have  been  on  hand  December  1st  to 
maintain  the  supply,  and  that  the  capacity  of  the  cistern 
must  have  been  at  least  543  cubic  feet;  or  552  cubic  feet  if 
all  the  water  received  was  to  be  stored.  The  contents  on 
the  first  of  each  month  would  then  be  as  follows: 


RAINFALL. 


85 


Dec. 

Jan. 

Feb. 

Mar. 

Apr. 

May. 

June. 

July. 

Aug. 

Sept. 

Oct. 

Nov. 

410.48 

542-67 

409.86 

3S3-72 

389.25 

333-" 

119.47 

0.00 

386.36 

55J-88 

384.91 

271.27 

Cisterns  for  private  supply  have  generally  a  capacity  of 
500  to  50,000  gals.,  5000  gals.  (667  cubic  feet)  being  a  very 
good  size  for  average  cases.  An  underground  cistern  should 
be  absolutely  tight,  having  no  openings  except  for  the  pump- 
suction  and  rain-water  leader,  and  a  ventilator  or  air-escape 
which  cannot  be  entered  by  mice  or  other  animals.  Where 
the  strength  of  the  building  is  sufficient,  a  tank  on  the  top 
floor  is  generally  a  more  convenient  and  better  arrangernent, 
as  affording  inspection  and  freedom  from  contamination,  and 
delivering  the  water  under  a  head ;  but  the  water  is  warmer 
in  summer  than  if  an  underground  cistern  be  used.  Two 
circular  tanks,  each  8.4  feet  diameter  and  6  feet  high,  will 
hold  5000  gals. 

The  daily  consumption  of  50  gals,  referred  to  allows,  for 
a  family  of,  say,  six  persons,  but  8  gals,  per  capita  per  day, — 
an  amount  which  does  not  permit  of  the  use  of  indoor  sani- 
tary appliances;  and  a  much  larger  supply  is  desirable  for 
hygienic  reasons  as  well  as  those  of  convenience. 

Art.  28.     Summary.     Estimating  Future  RainfalL: 


Estimates  of  future  rainfall  must  be  based  upon  the 
records  of  past  precipitation.  These  should  cover  as  long  a 
period  as  possible,  and  estimates  based  upon  the  records  of 
two  or  three  years  only  can  be  but  approximate  and  tentative. 
Where  there  are  no  long-period  records  for  the  locality  in 
question,  all  available  ones  of  that  precipitation  district 
should  be  consulted,  and  especially  of  those  places  nearest 
and  having  the  most  nearly  similar  location  as  regards  eleva- 
tion and  surrounding  topography. 


S6  WATEIi-SUFPLY  ENGINEERING. 

It  will  be  noticed  that  of  all  Weather  Bureau  stations  in 
the  North  Atlantic,  Ohio,  and  West  Gulf  States  (District 
No.  i)  none  has  a  precipitation  rate  more  than  32,'^  less  than 
the  district  average;  and  in  District  No.  2,  28^  is  the  greatest 
amount  by  which  any  rate  falls  below  the  district  average. 
In  District  No.  3,  excluding  the  Missouri  valley,  18^  is  the 
greatest  amount;  in  District  No.  4,  35^;  in  District  No.  7, 
22^;  and  in  District  No.  8,  38,^  is  the  greatest  amount  by 
which  any  rate  falls  below  the  district  average.  In  the 
Plateau  (Districts  Nos.  5  and  6)  there  is  great  variation  in 
rates,  even  within  the  limits  of  one  State;  and  still  greater 
variation  may  be  discovered  as  more  stations  are  added,  there 
being  now  but  thirteen  in  this  district. 

In  a  new  country  much  can  be  learned  by  the  character 
of  vegetation,  size  of  streams,  evidence  of  past  freshets,  etc., 
as  to  whether  the  average  precipitation  is  great  or  small,  and 
what  relation  it  bears  to  that  which  is  observed. 

In  figuring  upon  the  sufficiency  of  a  given  supply  the 
water-works  engineer  is  most  concerned  in  the  viinimtini 
monthly,  yearly,  and  dry-cycle  rates;  the  maximum  having 
little  bearing  except  upon  the  methods  of  controlling  and 
wasting  the  surplus.  Periods  of  drought  seem  to  occur  at 
intervals  of  four  to  ten  years  throughout  the  country,  but  no 
law  of  their  recurrence  has  been  formulated,  nor  do  the 
records  seem  to  suggest  any  such;  and  the  only  practicable 
method  seems  to  be  to  base  the  design  upon  the  dryest  cycle 
recorded  for  that  district,  or  on  an  even  lower  rate  if  the 
record  covers  less  than  thirty  or  forty  years. 

QUERIES. 

6.  Calculate  the  size  of  tank  required  in  New  York,  and  the 
amount  necessary  to  be  contained  in  it  on  Dec.  i,  1879,  if  it  is  to 
supply  up  to  Dec.  i,  1881,  75  gallons  per  day,  receiving  the'  rainfall 
on  a  roof  of  1400  sq.  ft.  area,  \  in.  per  month  of  which  rainfall  is 
wasted. 


RAINFALL.  8/ 

7.  In  case  a  rainfall  of  one  inch  entirely  cleared  all  soot  and 
ammonia  from  the  air  of  Cleveland,  O.,  when  it  contained  the 
amounts  of  these  found  by  Mabery  in  his  first  analysis  (page  56), 
what  quantities  of  matter  in  suspension  and  of  ammonia  would  be 
contained  in  the  rain-water,  in  parts  per  100,000  ?  These  impurities 
being  considered  to  permeate  the  lower  100  feet  of  the  atmosphere. 

S.  From  the  Philadelphia  records,  arrange  the  months  in  the 
order  of  probable  drought  ;  that  is,  place  first  the  month  in  which  a 
drought  is  most  likely  to  occur,  and  last  that  in  which  it  is  least 
likely. 


CHAPTER   VI. 
SURFACE-WATERS. 

Art.  29.     Evaporation. 

If  all  the  precipitation  upon  a  given  area  reached  the 
streams  draining  it  as  run-off,  the  calculation  of  the  amount 
of  the  latter  would  be  simply  finding  the  product  of  the  total 
watershed  by  the  precipitation.  But,  as  has  been  stated, 
much  of  the  precipitation  returns  to  the  air  by  evaporation. 
Since,  however,  all  but  a  very  minute  portion  of  the  rainfall 
on  a  given  watershed  which  does  not  leave  it  as  evaporation 
leaves  it  ultimately  as  yield,  it  would  seem  as  though  the 
latter  might  be  obtained  by  taking  the  difference  between 
the  total  precipitation  and  the  total  evaporation;  and  C.  C. 
Vermeule,  as  consulting  engineer  for  the  New  Jersey  State 
Geological  Survey,  deduces  a  method  of  calculating  yield  in 
this  way.  There  remains,  however,  the  difficulty  of  deter- 
mining the  evaporation.  The  amount  of  evaporation  depends 
upon  the  degree  of  dryness  of  the  air,  the  temperature  of  the 
air  and  of  the  soil  or  water  from  which  the  evaporation  takes 
place,  upon  the  amount  of  moisture  in  the  soil,  and  upon  the 
force  of  the  wind.  Most  measurements  of  evaporation  have 
been  made  from  water-surfaces  or  by  an  evaporometer;  the 
Piche  being  the  evaporometer  most  used  in  this  country 
Water-surfaces  form  but  a  small  proportion  of  the  total  areas 
of  most  catchment-basins,   but   the    amount   of    evaporation 


SURF  A  CE-  WA  TEES. 


89 


from  these  and  from  the  reservoirs  themselves  can  be  ascer- 
tained much  more  accurately  than  that  from  earth  and 
vegetation.  The  following  tables  give  the  evaporation  from 
water-surfaces  at  a  number  of  places  in  this  country. 

Table  No.  27. 
evaporation  from  water-surfaces,  in  inches. 


Location. 


Boston,  Mass 

Sweetwater,  Cal 

Rochester,  N.  Y 

Middle  Atlantic  States . 

South  Atlantic  States 

East  Gulf  States 

West  Gulf  States 

Ohio  Valley  and  Tennessee. 

Lower  Lake 

Upper  Lake 

Upper  Mississippi 

Extreme  Northwest 

Yuma,  Ariz 

San  Diego,  Cal 


Monthly. 


Max.        Min.      Mean 


7.50  0.66 
9.02  0.25 
6.20        1. 51 


3-29 
4-51 
2.61 


Max. 


43-63 
58.65 

34-4 
48.1 
51.6 
56.6 

52.4 
54.8 
38.6 
36. 3 
52.2 
31.0 


Min.      Mean. 


34-05 

48.68 

30.0 

25.2 

38.4 

45-4 

45-6 

44-5 
32-9 
23.0 
28.1 
22.1 


Table  No.  28. 
evaporation  from  water-surfaces,   by  months. 


Duration 
of  Obser- 
vation. 

c 
0.96 

1.05 

1.70 

a 
< 

2.97 
3.12 

2.78 

4.46 
5.82 
3-f^3 

4.46 
5'89 
3-35 

4.96 
6. ,4 

3-45 

c 

3 

5-54 
7.01 

3-94 

5.41 
7-3° 
3-19 

3 

5-98 
7.50 
4.82 

6-43 
8.81 
3.16 

3 
< 

5-50 
7-41 
4-25 

6.74 
9.02 
3.07 

5. 
to 

4.12 

513 

3.08 

5-96 
7.36 
4.64 

0 

316 
4-13 

2-5' 

4-77 
6.56 
3.00 

> 

0 

2.25 
3.00 
0.66 

4-5I 
5-53 
3-35 

u 

Boston 

16  years. 

Mean 

Maximum.. 
Minimum. . 

Mean 

Maximum.. 
Minimum. . 

1.51 

2.6g 
3.61 
i-SQ 

2.41 

3-53 
1-35 

2.86 
3.38 
1.08 

Sweetwater.. 

7  years. 

2.68 
6.28 
0  25 

Of  the  Sweetwater  data  those  for  the  first  four  years  were 
gauged  in  a  pan  floating  in  the  reservoir  (see  Fig.  3);  for  the 
last  three  years  by  a  Piche  evaporometer.  Both  this  and  the 
Richards  evaporation-gauge  are  thought  by  some  to  give 
inaccurate  results,  since  they  are  affected  by  the  temperature 
of  the  air  only,  which  is  seldom  the  same  for  any  length  of 
time  as   that   of  a   near   body   of  water.     A  more  accurate 


90 


WATER-SUPPLY  ENGINEERING. 


method  would  seem  to  be  to  measure  the  actual  loss  from  a 
pan  filled  with  water  and  floating  in  a  lake  or  other  body  of 
water.  Such  a  pan  and  scale  are  shown  in  Fig.  3.  Owing 
to  the  protection  from  wind  offered  by  the  sides  of  the  pan, 


Fig.    3.  —  EVAPORATING-PAN. 

this  probably  gives  results  slightly  less  than  the  evaporation 
from  lake  or  pond  surfaces. 

Evaporation  is  seen  to  vary  less  than  does  rainfall,  the 
greatest  variation  from  the  annual  mean  at  Boston  during 
sixteen  years,  for  instance,  being  about  13^. 

The  ratio  of  the  mean  monthly  to  the  mean  annual  evap- 
oration at  each  place  is  shown  in  Table  No.  29,  as  well  as  the 
monthly  ratios  for  the  year  of  maximum  evaporation  at  each 
place. 


S  URFA  CE-  IV A  TERS.  9 1 

Table  No.  29. 

ratios  of  monthly  to  mean  annual  evaporation  from 
water-surfaces  at  boston  and  sweetwater. 


a 

< 

rt 

c 

3 
1—. 

3 

ti 

3 

<! 

a 

0 

>' 

0 

.025 
.050 
.022 
.043 

.027 
.045 
.024 
.023 

.043 
•053 
•039 

.052 

.076 
.083 
.069 
.098 

.114 
.092 
.086 
.079 

.141 
.100 
.161 
.109 

•IS3 
.120 
.162 
.148 

.141 
.125 
.170 
.110 

•  105 

.  HI 

.117 
.105 

.080 
.088 

.064 
.110 

•  057 
.083 
.051 
.080 

.038 
.050 
■035 
.043 

Sweetwater,  mean  monthly  rate 

Boston, monthly  rate, year  of  mai.evap. 
Sweetwater,"        "        '"     "  "           " 

These  two  places  represent  almost  the  extremes  of  the 
United  States,  and  the  monthly  ratios  for  almost  any  locality 
will  He  between  these  as  limits.  It  will  be  noticed  that  the 
ratios  are  much  more  uniform  on  the  Sweetwater  basin  than 
in  Boston,  owing  largely  to  the  more  uniform  temperature 
throughout  the  year;  also  that  in  Boston  the  excessive 
evaporation  during  the  year  of  total  maximum  occurred 
between  June  and  September,  and  on  the  Sweetwater  basin 
between  June  and  October — that  is,  during  the  warmest 
weather. 

The  evaporation  from  snow  was  found  at  Boston  to 
average  .02  inch  per  day;  and  that  from  ice  .06  inch  per  day. 
On  exposed  mountain  sides  and  tops  it  would  probably 
exceed  these  averages. 

Still  more  important  than  the  evaporation  from  water  is 
that  from  soils  of  different  characters;  but  very  few  reliable 
data  on  this  subject  have  been  obtained.  The  amount  of 
water  taken  up  by  vegetation  is  important,  but  on  this  sub- 
ject also  very  little  definite  information  is  available. 

Experiments  at  Rothamsted,  England,  showed  the  annual 
evaporation  from  bare  soil  to  be  17.09  inches  when  the 
average  rainfall  was  31.04  inches;  and  of  the  13.95  inches 
percolating  through  the  soil  9.44  inches  was  collected  between 
October  and  March,  and  4.51  inches  during  the  seven  warmer 
months. 


92 


WA  TER-SUPPL  V  ENGINEERING. 

Table  No.  30. 
evaporation  from  grass  and  earth. 


c 

a 

< 

c 

3 

"5 

3 
< 

!/3 

0 

0 

> 

0 

Q 

rt 

u 

>< 

From  short  grass  at   Emdrup, 

Denmark;  8  years 

0.7 

0.8 

1.2 

2.6 

4.1 

.s-s 

5-2 

4-7 

2.8 

1-3 

0.7 

O.J 

30.1 

From  water  during  same  time. 

0.7 

0.5 

o.q 

3.0 

.3-7 

.5-4 

5.2 

4.4 

2.6 

'•3 

07 

0.5 

27.9 

From  long  grass,  same  time.. .. 

0.9 

0.6 

1.4 

2.6 

4-7 

b.7 

9-3 

7-9 

5-2 

2.9 

••3 

0.5 

44.0 

Evaporation     from     earth      at 

Bolton    Le   Moor,    England; 

lo  years 

0.64 

o-QS 

i-.sq 

2 -.59 

4.38 

iM 

4.02 

3.06 

2.02 

1.28 

0.81 

0.47 

25-65 

Evaporation      from    earth     at 

Whitehaven,  Eng.;  lo  years.. 

0.95 

I.OI 

1.77 

2.71 

4. II 

4-25 

4.13 

3.29 

2.96 

1.76 

1-25 

1.02 

29.31 

Table  No.  31,  from  the  Report  of  the  Kansas  State  Board 
of  Agriculture  for  1889,  shows  the  result  of  experiments  on 
consumption  of  water  by  various  crops.  From  this,  grasses 
and  grains  would  appear  to  consume  about  .12  inch  or  .14 
inch  per  day,  vineyards  and  potatoes  about  .03  to  .04  inch. 

Table  No.  31. 

DAILY    CONSUMPTION    OF    WATER    BY    CROPS.        (rISLER.) 


Inches. 

Inches. 

Lucerne  grass 

Meadov?  grass 

Oats 

0.134  to  0.267 
0.122  to  O.2S7 
0.140  to  0.193 
O.III  to  1.570 
0.140 
0.035  to  0.031 

Wheat 

Rye 

Potatoes 

0.106  to  O.IIO 

0.091 

0.038  to  0.055 

0.038  to  0.030 

0.020  to  0.043 

Indian  corn 

Oak  trees 

Fir  trees  

In  Western  irrigation  it  is  considered  necessary  to  use 
from  18  to  24  inches  of  water  per  year,  not  all  of  which, 
however,  is  taken  up  by  the  crops;  but  which,  on  the  other 
hand,  is  in  addition  to  the  rainfall.  The  crop-consumption 
of  water  extends  over  about  six  months  only  in  the  temperate 
zone.  If  from  i  inch  (for  forests)  to  6  inches  (for  grass)  per 
month  is  taken  up  by  vegetation,  or,  say,  an  average  of 
4  inches  (the  amount  required  for  cereals)  during  six  months 
of  the  year,  it  is  apparent  that  during  that  time  much  of  the 


S  VRFA  CE-  IV A  TEJiS. 


93 


rainfall  upon  areas  so  cultivated  would  be  thus  absorbed.  It 
is  probable  that  there  is  little  evaporation  directly  from  the 
soil  in  such  areas;  the  values  in  Table  No.  30  probably 
including  the  total  loss  by  evaporation  and  vegetable  absorp- 
tion. This  apparently  is  further  shown  by  the  fact  that 
evaporation  from  woodland  soil  is  found  to  be  but  35  to  40 
per  cent  as  great  as  that  in  the  open. 

The  above  tables  of  soil-evaporation  and  vegetable- 
absorption  should  not  be  considered  as  being  in  any  great 
degree  accurate.  The  only  method  at  all  accurate  which  has 
so  far  been  employed  for  ascertaining  on  a  large  scale  the 
amount  of  moisture  thus  withdrawn  from  the  yield  is  that  of 
measuring  the  stream-flow  and  deducting  this  from  the  total 
rainfall.  Since  the  evaporation  is,  so  far  as  the  water-works 
engineer  is  concerned,  in  most  cases  a  means  and  not  an  end, 
the  only  benefit  to  him  from  this  method  lies  in  the  oppor- 
tunity offered  for  studying  the  evaporation-value  thus  found 
in  its  relation  to  other  known  phenomena,  and  learning  the 
controlling  laws.  By  this  method,  comparing  data  from  a 
large  number  of  rivers  and  their  watersheds,  Vermeule 
deduced  the  formula     (for  New  Jersey  only) 

E=  (i5.5  +  .i67^)(.05r-  1.48), 

in  which  E  is  the  annual  evaporation  (including  vegetable 
absorption),  R  the  annual  rainfall,  and  T  the  mean  annual 
temperature.  The  monthly  evaporation  he  represents  by  the 
following,  in  which  r  is  the  monthly  rainfall: 


January. 

February. 

March. 

April. 

May. 

June. 

.27  +  .lOr 

.30  +  .lOr 

.43  +  .lOr 

.87  +  .lOr 

1.87  +  .20r 

2.50  +  .25r 

July. 

August. 

September. 

October. 

November. 

December. 

3.00  +  .30r 

2.62  4- .25r 

1.63  -j-  .20;- 

.88  +  .I2r 

.66  +  -lor 

.42  +  -10^ 

94  WATER-SUPPLY   ENGINEERING. 

This  formula  seems  to  give  very  close  results  for  New 
Jersey,  eastern  New  York,  and  eastern  Pennsylvania  streams; 
but  is  inapplicable  to  many  sections.  For  instance,  applying 
^.his  to  the  basin  of  the  Sweetwater  River,  Cal.,  would  give 
an  annual  evaporation  5  to  15  inches  greater  than  the  rainfall. 
It  seems  probable,  nevertheless,  that  in  this  direction  lies 
the  best  method  for  calculating  probable  yield  of  a  water- 
shed. But  with  our  present  knowledge  and  data  the  only 
accurate  one  is  to  make  direct  measurements  of  the  stream- 
flow.  The  safest  rule,  where  this  is  impossible,  is  to  compare 
the  watershed  under  consideration  with  another  of  known 
yield  and  similar  in  all  or  most  of  its  characteristics,  including 
precipitation ;  bearing  in  mind  the  effect  of  variations  in  eleva- 
tion, temperature,  wind,  and  other  conditions  already 
referred  to. 

Art.  30.     Natural  Storage. 

There  is  another  factor  of  yield  which  affects  more  the 
periodic  than  the  total  yield,  although  it  has  considerable 
effect  upon  the  latter  also.  This  is  the  storage  in  the  ground 
of  water,  part  of  which  supports  vegetation,  and  part  slowly 
feeds  springs  and  streams;  and  in  ponds  of  surface-flow 
which  is  gradually,  though  more  quickly,  given  to  the 
streams.  A  part  of  the  water  so  stored  in  either  ground  or 
pond  is  evaporated;  but  a  considerable  proportion  of  the 
ground-water,  and  generally  of  the  pond-water  also,  reaches 
the  stream.  This  storage  is  not  only  an  important  factor  in 
maintaining  continuous  stream-flow  and  in  supporting  vegeta- 
tion, but  it  has,  as  stated,  some  effect  upon  the  total  yield, 
and  is  valuable  also  in  relieving  the  storage-reservoir  of  a 
considerable  portion  of  its  duty.  Where  there  is  little 
ground-storage,  as  on  dense  clay  land,  there  can  be  little 
vegetation,  largely  because  the  ground  contains  no  moisture 


S  UK  FA  CE-  WA  TERS.  9  5 

to  support  it;  and  since  little  water  soaks  into  the  ground, 
most  of  the  rainfall  runs  immediately  to  the  stream.  Where 
a  large  amount  soaks  into  the  ground  considerable  of  this  is 
taken  up  by  vegetation  through  its  roots  and  thus  abstracted 
from  the  yield.  We  might  therefore  expect  to  find  a  greater 
total  yield  from  a  rocky  or  clayey  soil  than  from  a  loamy  or 
sandy  one;  although  it  would  be  more  difificult  to  retain  the 
whole  for  use,  owing  to  the  great  quantity  flowing  off  in  a 
short  length  of  time. 

Not  only  does  ground-storage  develop  vegetation,  but 
vegetation,  by  loosening  the  soil  with  its  roots  and  obstruct- 
ing surface-flow,  develops  ground-storage;  and  hence  it 
follows,  both  as  cause  and  effect,  that  the  yield  from  a 
wooded  or  cultivated  soil  is  more  uniform  and  less  "flashy  " 
than  from  a  bare  one. 

The  water  which  percolates  into  a  soil  descends  to  a  more 
or  less  fluctuating  ground-water  level,  which  is  the  surface  of 
the  stored  water.  This  surface  slopes  in  the  direction  in 
which  the  ground-water  is  moving,  its  elevation  at  any  point 
being  governed  by  that  of  the  outlet  and  by  the  amount 
flowing  (the  greater  the  amount  the  greater  being  the  velocity 
of  flow  and  hence  the  slope);  the  slope  increasing  with  the 
fineness  and  density  of  the  soil  also.  (See  also  Art.  40.)  If 
a  stratum  of  impervious  material  lies  higher  than  the  eleva- 
tion at  which  the  ground-water  surface  would  otherwise  stand, 
the  ground-water  will  flow  above  this,  generally  with  greatei 
velocity  and  consequently  furnishing  less  storage  and  more 
varying  yield. 

Above  the  ground-water  surface  proper,  some  water  '\% 
held  in  the  soil  by  capillary  attraction  for  nourishing  plant 
life,  and  in  very  fine-grained  soils  the  amount  thus  retained 
may  be  considerable.  As  evaporation  removes  this  water 
from  the  top  soil,  capillary  attraction  draws  more  from  below, 
to  be  in  turn  evaporated ;  but  the  amount  of  water  which  can 


96  WA  TER-SUPPL  V   ENGINEERING. 

thus  be  raised  decreases  with  the  fall  of  the  ground-water 
surface,  and  thus,  when  the  interval  between  rains  is  long, 
the  upper  soil  becomes  thoroughly  dried.  The  next  rain 
must  then  renew  this  upper  supply  before  contributing  any 
water  to  the  run-off  storage.  "  If  the  rainfall  is  sufficient  to 
supply  the  evaporation  and  plant  growth,  the  flow  from 
ground-water  will  remain  constant,  because  the  head  which 
forces  it  through  the  rocks  and  gravels  is  constant.  When 
the  rain  is  insufficient,  the  head  will  be  drawn  down  and  the 
flow  will  decrease  at  a  certain  fixed  rate."  Once  the  draught 
upon  the  ground-storage  is  fairly  established  and  the  water 
drawn  down,  unless  the  rainfall  is  greater  than  it  usually  is 
in  summer  it  is  all  absorbed  by  the  dried  earth  and  does  not 
reach  down  far  enough  to  increase  the  head  and  consequent 
flow  of  ground-water.  "  Rainfalls  which,  if  occurring  in 
May,  or  in  the  autumn  after  the  ground-water  has  been 
replenished,  would  cause  violent  floods,  have  no  effect  at  all 
upon  the  stream-flow  when  they  occur  during  dry  months. 
This  difference  in  effect  cannot  be  ascribed  to  direct  evapora- 
tion, for  in  the  case  of  concentrated  rainfall  evaporation  has 
little  time  to  act.  It  is  due  to  the  drawing  down  of  ground- 
water, which  leaves  a  great  capacity  for  absorption  of  rain  by 
the  earth."  (Vermeule's  Report  on  "  Water-supply,  Geo- 
logical Survey  of  New  Jersey.") 

The  absorption-capacity  varies  with  different  soils,  and 
also  the  amount  of  water  yielded.  A  coarse  gravel  will  yield 
almost  its  entire  contents,  while  fine  sand  or  clay  will  yield 
practically  none,  retaining  it  all  by  capillary  attraction.  The 
table  on  page  97,  from  Schubler,  gives  results  obtained  from 
various  soils. 

From  this  table  it  would  appear  that,  given  the  same 
conditions  as  to  vegetation,  exposure,  climate,  etc.,  the 
evaporation  from  all  soils  would  be  quite  similar. 

The  subsoil  in  twenty-three  localities  in  South  Carolina 


SURFA  CE-  WA  TERS. 


97 


and    Maryland  was   found   to   contain  from   37.2   to  65.1    per 
cent  by  volume  of  voids,  with  a  mean  of  48.73^. 

Table  No.  32. 
capacity  for  absorption  and  yielding  up  of  water  possessed 

BY    VARIOUS    SOILS.       (fROM    SCHUBLER    BY    VERMEULE.) 


Soil. 


Water  absorbed 

by  100  parts  of 

soil  after  drying 

at  40°  or  50* 

Kahr. 


Percentage  of 
water  evapo- 
rated in  4  hours 
at  56.7°  Fahr. 


Parts    of  water 

in  100  parts  of 

soil  evaporated 

in  4   hours  (soil 

saturated). 


Siliceous  sand 

Gypseous  soil 

Calcareous  sand 

Barren  clay 

Fertile  clay 

Loamy  clay  (or  clayey  soil) 

Pure  clay 

Fine  calcareous  soil 

Humus 

Magnesian  soil 

Garden  soil 


25 
27 
29 
40 
50 
60 
70 

85 
190 
156 


75-9 
52 

45-7 
34-9 


22 
21 

23 
21 


28.6 
20.2 


24 
3S 


The  least  flow  of  the  Connecticut  River  is  equivalent  to 
about  .05  cubic  feet  per  second  per  square  mile  of  watershed, 
which  is  maintained  during  probably  a  month  at  least  of  no 
rainfall  and  three  months  when  the  rainfall  no  more  than 
equals  the  evaporation  and  requirements  of  vegetation.  The 
flow  must,  during  this  time,  be  maintained  by  the  ground- 
water storage,  and  is  equivalent  to  about  1.7  inches  of  water 
over  the  entire  area.  If  the  soil  furnishing  ground-storage 
averages  an  absorption-capacity  of  'Hfc,  the  ground-storage 
surface  would  be  lowered  about  5  inches  on  an  average. 
But  not  all  the  ground  furnishes  storage,  and  probably  not 
more  than  50^  of  that  held  is  yielded  to  the  stream;  also  the 
lowering  increases  with  the  distance  from  the  river,  so  that 
in  some  places  it  may  amount  to  3  feet  or  more. 

In  a  fairly  wet  or  rainy  season  the  ground- water  surface 
may  be  raised  5  or  10  feet,  even  reaching  the  surface  in 
many  places  and  producing  ponds  or  swamps. 


98  WATER-SUPPLY  ENGINEERING. 

Most  storage-reservoirs  have  not  water-tight  shores,  and 
as  the  water  rises  in  the  reservoir  the  ground-water  level  in 
the  vicinity  rises  also,  and  ground-storage  is  obtained  in 
addition  to  that  in  the  reservoir.  When  the  reservoir  water 
is  drawn  down  this  ground-storage  also  is  drawn  upon,  and 
more  water  is  yielded  than  the  capacity  of  the  reservoir. 

Art.  31.     Yield  or  Run-off. 

The  yield  is  the  total  rairifall,  less  the  amount  consumed 
by  vegetation  and  evaporated,  and  it  is  regulated  in  its  final 
delivery  by  ground-storage.  All  of  these  factors  and  the 
relations  between  them  are  as  yet  but  partly  understood,  and 
the  data  concerning  them  are  scant  in  many  localities.  The 
most  common  method  of  estimating  yield  is  to  assume  it  to 
be  a  certain  percentage  of  the  rainfall — generally  about  50^ 
in  the  eastern  part  of  the  country;  but  this  assumes  the  rain- 
fall to  be  the  only  factor,  which  it  is  not,  and  also  requires 
the  estimating  of  the  percentage  of  yield.  The  amount  of 
yield  varies  with  the  climate,  the  surface  and  subsurface 
structure  and  conditions,  the  meteorological  conditions  before 
and  after  each  rain,  and  other  causes.  On  the  Sudbury 
watershed,  for  instance,  the  amount  of  rainfall  reaching  the 
streams  during  the  seven  months  from  November  to  May 
inclusive  is  large,  while  from  June  to  October  it  is  small;  the 
greatest  stream-flow  being  in  February,  March,  and  April. 
The  annual  yield  of  this  shed  has  varied  from  31.9  to  62.2 
per  cent  of  the  precipitation,  the  mean  for  sixteen  years  being 
49.5^.  "  The  percentages  depend  upon  the  distribution  of 
rainfall  throughout  the  year.  A  heavy  summer  rainfall  and 
a  light  winter  rainfall  mean  a  small  percentage  of  collection ; 
and,  conversely,  a  light  summer  and  a  heavy  winter  rainfall 
mean  a  large  percentage  of  collection ;  so  that  the  total  rain- 
fall for  the  year  is  but  a  partial  index  to  the  yield  of  a  water- 


SUJiFA  CE-  WA  TERS. 


99 


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WA  TER-SUPPL  Y  ENGINEERING. 


shed."  "It  may  be  said  that,  for  systems  which  depend 
upon  storage,  it  is  not  the  summer  droughts  which  are  to  be 
dreaded,  but  the  winter  and  spring  droughts;  for  it  is  the 
flow  in  these  months  upon  which  we  depend  to  fill  the  reser- 
voirs." (Desmond  FitzGerald,  in  Transactions  of  American 
Society  of  Civil  Engineers,  vol.  xxvii.) 

In  California  the  amount  collected  annually  may  vary 
from  nothing  when  the  rainfall  is  less  than  20  inches,  to  60;^ 
in  years  of  heavy  rainfall,  averaging  not  far  from  30^.  In 
Southern  California  the  average  for  seven  years  was  10.6^. 
Table  No.  33  shows  the  run-off  from  a  number  of  water- 
sheds, expressed  in  percentages  of  the  rainfall.  In  the  case 
of  the  Potomac  basin  the  December  percentages  varied 
between  18  and  24,  and  the  annual  percentages  between  30.0 
and  58.2.  On  the  Sudbury  watershed  the  December  per- 
centage varied  during  sixteen  years  between  9.6  and  264.4 
per  cent,  and  the  annual  between  31.9  and  62.2  per  cent, 
and  the  annual  on  the  Cochituate  between  25.7  and  69.1  per 
cent. 

The  following  table  shows  the  maximum  and  minimum 

yield  for  two  watersheds: 

Table  No.  34. 

maximum,  minimum,  and  mean  yield:   connecticut  and 
potomac  watersheds. 


Connecticut  Rivek,  13  yrs. 

Rainfall,    inches  depth 

Max.  yield,     "  "      

Min.      "  "  "      

Mean     "  ':  "      

Mean  percentage  yielded 

Potomac  River,  6  years. 

Rainfall,  inches  depth 

Max.  yield,  sec.  ft.  per  sq.  mi. 
Min.       "        "      "     "     "     " 
Mean     "        "      "     "     "     " 
Mean  percentage  yielded   . . . 


3-27 
5.70 
0.72 
1.93 
59.1 


3.21 
14.00 


3.10 
4.06 
0.77 
2.04 
65.8 


3-35 
15.81 
0.22 

3-22 

98.5 


3-94 
5.64 
0.90 
3.0' 
76.3 


4-39 
17.10 
0.25 
3-'4 
84.9 


3.26 
7.61 
2.61 
4-73 
•45-0 


20.87 
0.25 
3-15 

104 


3.17 
6-54 
1 .90 
4.19 
132.2 


0.23 
2.04 
44-7 


4.00 
3. II 

0.79 
1 .46 
365 


4-79 
2.32 
0.69 


4 

19.36 
0.25 
0.87 

23.1 


4.87  3.C4 
2 .52  2.24 
0.70  0.66 
1.06  0.89 
21.8:29.3 


3.81:3.86 

5-94  7-63 

0.27 

0.67 


21-3 


0.27 
0.95 
25.0 


3-93 
2.81 
0.71 
I. II 
28.3 


2.65 

14.50 

0.27 

1.07 

40.5 


3-9313-39 

3.60j4.93 

0.67  jo. 72 

I .7612.06 

44.8     60.7 


2.88  2.59 

5.25I9.48 
3.27  ,0.27 
i.6i|i.i5 
♦■3    |72-3 


SURF  A  CE-  WA  TEES. 


lOI 


From  examples  of  such  wide  variation  it  is  evident  that 
the  use  of  a  mean  percentage  of  the  rainfall  for  estimating 
the  run-off  will  give  only  very  approximate  results;  particu- 
larly since  the  lowest  percentages  usually  occur  during  the 
years  of  minimum  precipitation.      (See  Figs.  4  and  5.) 


1875      1877      1879      1881      1883"     1885      1887      1889   1890' 

Fig.  4. — Precipitation  and  Percentage  Collected;  Sudbury  Water- 


percentage 

AND  INCHESi 
OF  RAINFALL 


30 
20 

RAINFALL 

PERCENT. 

COLLECTED 

10 

0 

/ 

1 

\ 

\ 
\ 

\ 

- 

-::: 

:-^ 

^ 

/ 

\ 

"■^^, 

,.--''' 

/l 
/ 1 

1 
1 

1 
1 

\     N 
\ 

\ 
\ 
\ 
\ 

1888-89  1889-90     '    1890-91     "   1891-'93        1893--93        1893-'9t         1894-'95        1895-'96 

Fig.   5. — Rainfall  and  Percentage  Collected  ;  Sweetwater  Basin. 

Run-off  is  sometimes  expressed  in  cubic  feet  per  second 
per  square  mile,  as  in  Tables  Nos.  34,  35,  and  36.  Since 
run-off  is  a  product  of  the  rainfall  and  the  percentage  of  this 
reaching  the  streams,   the  records  of    stream- flow  might  be 


I02 


WATER-SUPPLY  ENGINEERING. 


expected  to  show  greater  variation  than  either  of  these,  which 
is  seen  to  be  the  case. 

Table  No.  35. 
run-off  from  several  drainage-basins, 


Watershed. 


Sudbury. . .  • 
Connecticut 

Croton 

Perkiomen  . 

Raritan 

Passaic 

Potomac.  .  .  . 
Savannah  . . 

Ohio 

Missouri. .  • . 
Arkansas. . . 
Rio  Grande. 

Gila 

West  Carson 
Sevier  (Utah 


Length 
of 
Observa- 
tion, 
Years. 


I6 
15 
14 

7 
I 

17 
6 


12 
5 
3 
I 
2 
3 


Area, 
Sq.  Mi. 


75-199 
10,234 

353 
152 
879 

773 
11,043 

7.294 

200,500 

526,500 

3,060 

30,000 

13.750 

70 

5.595 


Run-off,  cu.  ft.  per  sec.  per  sq.  mi. 


44.26 
20.00 
75.22 
69.20 
27.00 
24.80 
42.60 
41  .  2 
6.17 
8.52 

1-55 
0.55 
0.46 

18.34 
0.42 


Min. 


0.04 

0.15 
0.05 
o.  14 

0.17 
0.17 

0.27 
0.27 
0.60 
0.06 
0.00 
0.00 
0.50 

O.OI 


Mean. 


1 .669 

1.86 

1.65 

1.90 

1.72 

2.58 

1.85 

1.64 

2.10 

2.16 

0.27 

0.06 

0.04 

2-39 
0.09 


Table  No.  36. 
ratio  of  monthly  to  mean  annual  run-off. 


c 

1.866 
1 .20 

1. 15 

v 

c5 

a 
< 

V 

c 

3 

"3 

bib 

3 
< 

a. 

V 
(/3 

0 

Nov. 
Dec. 

c 

V 

Mean  of  3  New 
England  water- 
sheds for  13  years, 
cu.  ft.  per  sec. 
per.  sq.  mile 

Ratio  of  monthly 
to  mean 

Boston, for  20  years, 
ratio  of   monthly 

3.042 

1.97 

1.80 

3-555 
2.31 

2.68 

2-533 
..65 

1. 91 

I-5I8 

o.gS 
1 .10 

0.772 
0.50 

0.46 

0-374 
0.24 

0.17 

0.569 
0.36 

0.28 

0.528 
0.34 

0.23 

0.838 
0.54 

0.47 

1.278 
0.83 

0.81 

1.703 
1. 10 

0.94 

1-539 
1.644 

That  the  run-off  per  square  mile  from  two  watersheds 
should  be  the  same,  it  would  be  necessary  that  they  be 
similar  in  shape,  in  ground  slope,  in  soil,  in  amount  and 
character  of  wooded  and  cultivated  areas,  in  area  of  ponds, 
and  that  the  wind  movements  and  humidity,  as  well  as  the 


S  URFA  CE-  IV A  TERS.  I O  3 

rainfall,  be  similar  in  both ;  since  all  these  factors  affect  the 
run-off.  Two  adjacent  watersheds  may  differ  greatly  in  some 
of  these  conditions,  and  hence  in  yield.  For  instance,  we 
find  the  proportion  of  rainfall  yielded  by  three  Pennsylvania 
watersheds  within  a  few  miles  of  each  other  to  vary  as  51.6, 
48.7,  and  59.6  (Table  No.  32),  or  a  difference  of  22^  between 
extremes.  Two  adjacent  Massachusetts  watersheds  varied  in 
percentage  of  yield  by  12^^,  or  as  49.5  and  43.8.  In  central 
California  the  mean  yield  is  not  far  from  30<^  of  the  precipita- 
tion, while  in  the  southern  part  of  the  same  State  the  mean 
for  seven  years  was  but  10.6^. 

Although  these  data  show  a  great  variation  in  percentage 
of  rainfall  yielded  in  different  parts  of  the  country,  and  in 
different  years  on  the  same  watershed,  the  average  yield  in  a 
given  section  of  country  is  fairly  uniform.  For  instance,  in 
the  New  England  and  Central  Atlantic  States  the  yield 
generally  averages  from  44  to  60  percent  of  the  precipitation, 
and  the  extreme  variation  in  any  one  place  is  about  2^ic  of 
its  mean,  so  that  the  use  of  the  average  rainfall  and  average 
percentage  yielded  would  very  probably  give  a  result  in  error 
not  more  than  30  or  40  per  cent.  Again,  if  we  compare  the 
second-feet  per  square  mile,  we  find  in  the  same  locality  a 
mean  yield  of  about  1.6  second-feet,  with  a  maximum  varia- 
tion from  this  of  about  40  to  50  per  cent.  By  using  judgment 
in  selecting  for  comparison  a  watershed  with  characteristics 
similar  to  the  one  in  question,  the  probable  error  may  be  re- 
duced in  many  cases  to  10  or  15  per  cent.  Below  this  it  is 
hardly  practicable  to  go,  except  by  obtaining  long-period 
records  of  yield  of  the  area  in  question. 

Since  the  evaporation  from  various  soils  is  practically  the 
same  if  the  affecting  conditions  be  similar  (see  Table  No.  32), 
and  likewise  that  from  water,  it  is  probable  that  the  relative 
run-off  per  square  mile  from  two  watersheds  similarly  located 
geographically  and  topographically  will  be  closely  related  to 


I04  WATER-SUPPLY  ENGINEERING. 

the  proportion  of  water-surface  on  each  area.  Thus,  know- 
ing the  yield  of  a  given  watershed  and  the  proportion  of 
water-surface  to  the  entire  area,  the  probable  yield  of  the 
ground-surface  alone  can  be  found  by  adding  to  the  total 
yield  of  the  entire  area  the  evaporation  from  all  water-surfaces 
and  deducting  the  rainfall  upon  the  same.  The  quotient 
found  by  dividing  the  result  by  the  area  of  the  watershed  in 
square  miles  will  be  the  approximate  yield  per  square  mile  of 
the  ground-surface.  This  can  then  be  corrected  for  any  given 
watershed  having  similar  characteristics,  by  adding  to  the 
yield  of  the  entire  area,  considered  as  a  ground-surface,  the  net 
yield  of  all  water-surfaces  on  this  area.  (See  the  table,  page 
117.) 

Where  no  watershed  with  similar  conditions  can  be  found, 
the  decision  must  be  a  more  or  less  arbitrary  one,  based  upon 
information  obtained  from  the  oldest  inhabitants,  observed 
stream-channels  and  ponds,  the  location  of  the  place  with 
reference  to  the  coast,  sea-level,  mountain-ranges,  etc.,  the 
character  of  soil  and  topography,  and  the  vegetation. 

The  measured  yield  of  the  area  in  question  for  a  long  series 
of  years  forms  of  course  the  most  reliable  basis  of  estimate; 
the  next  is  the  known  yield  of  similar  areas  in  the  same 
district ;  and  from  precipitation,  either  gauged  at  the  locality 
in  question  or  estimated  from  the  district  rate,  the  yield  may 
be  estimated  either  as  a  certain  percentage  of  this,  or  by 
deducting  the  probable  evaporation  according  to  Vermeule's 
rule  (page  93)  for  the  Eastern  States,  or  a  similar  one  formu- 
lated for  the  locality  in  question.  In  fact,  it  is  desirable  to 
estimate  by  each  of  these  methods  and  compare  results, 
giving  them  relative  weight  in  the  above  general  order. 

The  mean  yield  thus  obtained  can  be  made  the  basis  of 
estimating  the  volume  of  water-supply,  when  sufificient  storage 
is  provided  to  tide  over  a  number  of  dry  years;  but  when 
this  is  not  possible,  and  for  calculating  the  storage  necessary, 


S  URFA  CE-  WA  TERS.  I O  5 

the  minimum  and  maximum  yield  must  be  known  approxi- 
mately;  and  these  may  be  estimated  by  comparison  of  known 
data  in  the  same  way  as  the  mean  yield,  but  the  length  of 
time  covered  by  the  records  plays  an  even  more  important 
part. 

With  reference  to  yield  throughout  the  United  States  the 
general  statement  is  made  in  the  U.  S.  Weather  Bureau 
Reports  that  "  for  the  area  of  the  United  States  east  of  the 
95th  meridian  (Omaha  and  Galveston)  the  run-off  is  from  35 
to  50  per  cent  of  the  total  rainfall.  It  appears  to  be  largest 
in  the  vicinity  of  the  Great  Lakes,  and  diminish  from  this 
region  slowly  to  south  and  east,  and  rapidly  towards  the  west. 
In  the  lower  peninsula  of  Michigan,  for  instance,  the  run-ofif 
is  50^^  of  the  total  rainfall.  Along  the  Gulf  coast  it  appears 
to  be  only  from  30  to  40  per  cent,  and  along  the  Atlantic  coast 
it  probably  varies  from  30  to  50  per  cent.  In  general,  for 
the  interior  States  east  of  the  95th  meridian  the  run-off  is 
between  40  and  50  per  cent  of  the  total  rainfall. 

"  As  soon  as  we  cross  the  95th  meridian  westward  we  find 
a  very  sharp  fall  in  the  percentage  of  run-off  to  the  total 
rainfall.  For  the  band  extending  north  and  south  between 
the  95th  and  105th  meridians  this  percentage  varies  from  10  to 
25  percent,  and  over  Iowa  is  about  33/^.  The  percentage  is 
highest  at  the  northern  end  of  the  band  indicated,  and  lowest 
at  the  southern  end.  Going  still  farther  westward  we  come 
to  another  very  marked  area,  that  of  the  Continental  Divide; 
here  the  percentage  of  run-off  suddenly  increases,  reaching 
the  highest  figure  to  be  found  in  the  Upited  States.  From 
Montana  to  Colorado  it  varies  from  60  to  70  per  cent  of  the 
total  rainfall.  In  New  Mexico  it  falls  to  about  33;^.  This  is 
evidently  on  account  of  the  easy  flow  of  water  from  the 
mountain  ranges  in  the  area  in  question.  West  of  the  Divide 
the  run-off  is  again  small,  being  only  15  or  20  per  cent  in 
Arizona  and  Nevada,  about  30f»  in  Idaho,  and  nearly  50^  in 


106  WATER-SUPPLY  ENGINEERING. 

Utah.  Utah,  it  seems  from  its  topography,  partakes  of  the 
character  of  the  band  lying  just  to  the  east  of  it.  Along  the 
Pacific  coast  the  run-off  is  about  25^  in  Oregon,  30^  in  Wash- 
ington, and  between  45  and  50  percent  in  California"  (the 
northern  part  only). 

The  above  is  a  very  general  statement,  and,  particularly 
in  the  far  West,  is  subject  to  many  variations  and  exceptions, 
some  of  which  are  recorded  in  the  preceding  tables. 

(It  may  be  convenient  to  remember  as  an  approximation 
that  the  average  yield  of  New  England  watersheds  in  general 
ranges  between  300,000  and  600,000  gals,  per  day  per  square 
mile.) 

The  apparent  non-uniformity  of  the  data  relating  to  yield 
has  been  emphasized,  not  because  such  data  or  the  methods 
of  using  them  should  not  be  made  a  basis  for  estimating,  but 
to  call  attention  to  the  fact  that  the  estimates  cannot  be 
expected  to  give  more  than  general  and  approximate  results. 
When  the  data  are  meagre  or  unreliable,  any  works  based 
upon  them  should  be  more  or  less  tentative  in  design  and 
construction,  and  capable  of  being  modified  as  the  developing 
conditions  require. 

The  data  required  for  estimating  yield  will  be  found  in 
the  annual  Reports  on  Hydrography  of  the  U.  S.  Geological 
Survey,  the  Meteorological  Reports  of  the  Weather  Bureau, 
Reports  of  the  Geological  Surveys  of  New  Jersey  and  of 
several  other  States,  of  the  Departments  of  Agriculture  of 
several  Western  States,  and  the  Reports  of  the  water-works 
departments  of  various  cities,  particularly  in  the  New  England 
States. 

Art.  32.     Run-off  from  Storms. 

If  a  storage-reservoir  is  to  retain  all  the  yield  of  a  given 
area  it   must   be  sufficiently  large  to  hold  the  entire  run-off 


S  URFA  CE-  WA  TERS.  I O/ 

from  the  heaviest  downpours,  over  and  above  what  may  be 
already  stored  in  it  during  the  wettest  years.  Probably  no 
reservoir  has  been  constructed  to  do  this,  and  the  overflow 
must  therefore  be  capable  of  passing  the  maximum  storm 
run-off.  It  is  hence  necessary  to  know  what  the  maximum 
rate  of  run-off  from  the  heaviest  storms  will  be.  The  maxi" 
mum  run-off  from  large  drainage  areas  in  the  north  frequently 
occurs,  not  from  the  maximum  precipitation,  but  from  a 
heavy  warm  rain  falling  upon  a  ground  covered  with  con- 
siderable snow — the  spring  freshets.  At  this  time  about 
8  inches  of  snow  is  equivalent  to  one  inch  of  water.  Hence 
two  feet  of  snow  carried  off  in  24  hours  by  a  rain  would  add 
to  the  run-off  the  equivalent  of  3  inches  of  additional  rainfall 
running  off  in  that  time,  or  of  \  inch  per  hour  additional  to 
the  actual  precipitation,  if  all  of  the  latter  be  considered  to 
run  off.  Probably  the  addition  for  snow  of  i  to  ^  inch  per 
hour  to  the  run-off  from  the  rainfall  will  be  sufficient  for  most 
cases.  If  the  surface  under  the  snow  be  frozen  90^  or  more 
of  the  rainfall  may  be  yielded. 

The  maximum  rates  of  rainfall  generally  last  for  five  to 
fifteen  minutes  only.  Assuming  a  velocity  of  flow  over  the 
surface  of  2  feet  per  second  (probably  the  maximum  ordi- 
narily obtained),  and  in  the  stream  of  4  feet  (although  this 
may  reach  8  feet  per  second),  with  1000  feet  of  watershed 
above  the  head  of  the  creek,  at  the  end  of  15  minutes  of 
maximum  rainfall  the  first  r:  in  falling  at  the  head  of  the  basin 
would  have  travelled  2600  feet,  and  at  all  points  above  its 
position  at  that  time  the  run-off  would  be  that  due  to  the 
maximum  rate  of  rainfall.  But  at  all  points  more  than  2600 
feet  from  the  basin-head,  the  run-off  from  only  the  nearer 
part  of  the  basin  would  be  at  that  rate,  the  upper  part  con- 
tributing to  the  flow  at  a  rate  due  to  the  rainfall  previous 
to  the  beginning  of  the  maximum.  Thus,  at  3800  feet  from 
the  basin-head  the  flow  would  be  that  due  to  a  rainfall  for  a 


I08  WATER-SUPPLY  ENGINEERING. 

certain  five  minutes  on  the  upper  600  feet  of  basin,  for  the 
next  five  minutes  on  the  next  lower  800  feet  of  basin,  for 
the  next  five  minutes  on  the  next  lower  1200  feet,  and  for 
the  last  five  minutes  on  the  nearest  1200  feet  of  basin.  At 
any  point  in  the  run-off  channel  the  maximum  flow  will  be 
approximately  the  product  of  the  area  of  shed  above  such 
point,  the  maximum  average  rate  of  precipitation  for  the  time 
consumed  by  the  run-off  in  flowing  to  this  point  from  the 
most  distant  point  of  the  basin,  and  the  proportion  of  rainfall 
running  off.  The  determination  requires  a  knowledge  or 
assumption  of  the  proportion  of  rain  yielded  as  surface  flow, 
and  the  velocity  of  flow  of  the  maximum  run-off.  No  close 
approximation  to  this  latter  can  be  made  except  from  actual 
obervation  on  each  watershed.  The  run-off  from  heavy 
downpours  of  short  duration  may  be  60  or  70  per  cent  on 
steep  clay  or  stony  hillsides,  and  even  90^  or  more  on  rocky 
or  frozen  ground;  while  for  flat  slopes  of  loose  soil  30^  may 
be  the  maximum  amount. 

It  is  evident  that  the  larger  the  drainage  area  the  less  will 
be  the  rate  of  precipitation  used  and  hence  the  rate  of  run-off 
per  square  mile.  Distance  is  as  large  a  factor  of  this  rate  as 
is  area.  From  a  small  drainage-basin  10,000  feet  long,  with 
a  maximum  velocity  of  run-off  of  2  feet  per  second,  the 
lenffth  of  time  for  which  the  maximum  rate  of  rainfall  is  to 
be  considered  is  5000  seconds,  or  i  hour  23|-  minutes.  At 
Mt.  Carmel  on  July  2,  1897,  5.03  inches  fell  in  i^  hours. 
Assuming  this  as  a  maximum  rate  and  50^  running  off,  we 
have  a  run-off  of  1.68  cubic  feet  per  second  per  acre,  or  1075 
per  square  mile.  This  rate  of  precipitation — 3.36  inches  per 
hour — can  probably  be  considered  a  maximum  for  the  New 
England  and  North  Atlantic  States. 

Several  empirical  formulas  have  been  devised  to  express 
the  maximum  rate  of  run-off  from  a  given  area.  A  few  of 
these  are: 


S  URFA  CE-  WA  TERS.  1 09 

Fanning's  formula (2  =  200J/'; 

Dredges  "       (2  =  1300— ^  ; 

Col.  Dickens'  "       Q-  Cl/i ; 

in  which  Q  =  cubic  feet  per  second  yielded  from  the  whole 
area; 

M  =  area  of  watershed  in  square  miles; 

L  =  length  of  watershed  in  miles; 

C  =  200  in  flat  country,  250  in  mixed  country,  300 
in  hilly  country,  for  a  rainfall  of  3.5  to  4 
inches;   or  300  to  350  for  a  6-inch  rainfall. 

In  the  above  example,  if  the  watershed  contain  3  square 
miles,  being  1.9  miles  long,  the  maximum  rate  of  run-off  as 
calculated  by  the  above  formulas  would  be: 

by  Fanning,  Q  =     500  cu.  ft.  per  second; 

"   Dredge,  (2  =  2550    "     "  " 

"   Dickens,  Q  —     684    "    "  " 

"  above  solution,  Q—  3225    "    "  "         " 

As  the  size  of  the  drainage  area  increases  and  the  rate  of 
precipitation  used  consequently  decreases,  these  formulas 
will  give  quantities  more  nearly  approaching  those  obtained 
by  the  above  analytical  method,  and  when  an  area  20  or  25 
miles  in  length  is  involved,  that  of  Fanning  and  the  analytical 
method  would  give  approximately  similar  results.  But  for 
small  areas  the  above  formulas  will  generally  give  unsafe 
results,  and  the  method  outlined  is  recommended  for  design- 
ing waste-weirs. 

Art.  33.     Storage. 

In  Art.  27  was  given  an  illustration  of  the  reason  for 
storage  and  the  amount  required  for  private  use.  The  reason 
is  the  same  for  storing  public  supplies,  but  the  amount  stored 


no  WATER-SUPPLY  ENGINEERING. 

is  of  course  vastly  larger,  and  the  length  of  drought  provided 
for  is  usually  longer.  The  storage-reservoirs  for  the  San 
Francisco  water-supply  have  a  united  capacity  equal  to  the 
total  consumption  for  three  years.  In  the  East  two  thirds 
this  capacity  or  less  would  be  considered  suf^cient,  however,^ 
the  annual  precipitation  being  more  uniform. 

A  measurement  of  the  drainage  area  having  been  obtained^ 
and  a  decision  formed  as  to  the  probable  average,  minimum 
and  maximum  yield,  by  both  year  and  cycle,  and  the  con- 
sumption to  be  provided  for  being  determined,  a  calculatiorv 
of  the  storage  required  can  be  made.  If  the  minimum 
annual  yield  is  equal  to  or  greater  than  the  desired  consump- 
tion, storage  for  only  the  dry  season  of  one  year  of  drought 
is  required;  if  the  minimum  daily  yield  equals  the  maximum 
daily  consumption,  no  storage  is  required;  but  if  the  assumed 
consumption  is  nearly  or  quite  equal  to  the  mean  yield,  all  the 
surplus  from  the  years  of  greatest  rainfall  must  be  stored  and 
carried  until  times  of  drought.  In  many  cases  it  may  be 
advisable  to  construct  a  reservoir  in  such  a  location  or  of  such 
capacity  that  it  is  capable  of  tiding  over  one  dry  season  only, 
if  this  be  ample  for  the  consumption  for  a  few  years  to  come; 
and  when  the  capacity  of  the  reservoir  is  almost  reached  by 
the  consumption,  a  reservoir  of  larger  capacity  may  be  built, 
and  better  adapted  to  the  watershed  in  question  because 
based  on  data  meantime  collected;  the  interest  on  the  addi- 
tional sum  which  a  larger  original  reservoir  would  have  cost 
being  saved  during  this  period. 

In  making  the  calculation  for  storage,  evaporation  from 
the  reservoir  must  be  considered,  and  may  be  added  to  the 
consumption.  It  is  of  course  proportional  to  the  area  of 
water-surface  in  the  reservoir,  and  for  the  preliminary  calcula- 
tion this  area  must  be  assumed ;  usually  as  a  certain  propor- 
tion of  the  drainage  area,  which  relation  will  vary  with  the 
average  depth  of  the  reservoir,  and  this  with  the  nature  of 


A  URFA  CE-  IV A  TER5.  1 1 1 

the  ground  at  the  reservoir  site — whether  the  side  slopes  are 
more  or  less  abrupt.  In  the  New  England  and  Middle 
Atlantic  States  the  maximum  reservoir  required  would  have 
a  capacity  150  to  175  per  cent  of  the  mean  annual  yield.  An 
inspection  of  the  yield  for  a  series  of  years  at  any  location 
will  give  the  approximate  capacity  required  to  permit  the  con- 
sumption to  equal  the  average  yield.  This  capacity  divided 
by  the  average  depth  of  reservoir  will  give  its  area.  About 
one  tenth  that  of  the  drainage  area  may  be  considered  a  maxi- 
mum which  will  rarely  be  exceeded;  and  one  twentieth  may 
be  taken  as  an  average  maximum.  The  amount  of  evapora- 
tion in  cubic  feet  will  be  this  area  times  the  rate  of  evapora- 
tion, both  expressed  in  feet.  The  annual  rate  of  evaporation 
east  of  the  Mississippi  probably  never  exceeds  the  mean  rate 
by  more  than  10  or  15  per  cent,  although  in  the  Western 
States  it  may  by  30  or  35  per  cent.  (See  Table  No.  27,  page 
■89  )  To  be  on  the  safe  side  the  maximum  annual  rate  may 
be  used,  and  apportioned  to  the  months  if  monthly  yield  and 
consumption  are  to  be  used  in  the  estimate.  Table  No.  28, 
page  89,  gives  the  monthly  rates  for  Boston  and  Sweetwater, 
and  Table  No.  29,  page  91,  the  proportion  of  the  annual 
total  evaporation  occurring  each  month. 

The  maximum  evaporation,  annual  and  monthly,  area  of 
reservoir,  monthly  yield  and  consumption  (see  Table  No.  6, 
page  38)  having  been  decided  upon,  a  table  can  be  prepared 
similar  to  that  in  Art.  27,  the  monthly  consumption  and 
evaporation  being  combined  for  the  third  column,  and  yield 
substituted  for  precipitation  in  the  second.  In  estimating 
yield  it  should  be  borne  in  mind  that  all  the  rainfall  falling 
upon  the  reservoir  is  stored. 

On  the  Sudbury  basin  the  mean  evaporation  from  water 
was  171^  of  the  mean  yield.  Assuming  the  reservoir  area 
as  5V  ^^  watershed,  we  would  have  the  loss  by  evaporation 
about   8.5^  of  the  yield;   and  since  the  size  of  the  reservoir 


112  WATER-SUPPLY   ENGINEERING. 

will  vary  with  the  consumption,  which  cannot  exceed  the 
mean  yield,  we  may  assume  with  little  error  that,  on  similarly 
located  reservoirs,  the  evaporation  loss  from  the  reservoir  will 
not  exceed  8  to  lo  per  cent  of  the  consumption. 

There  will  be  some  loss  from  a  reservoir  due  to  seepage 
through  the  dam.  That  into  the  ground  may  be  considered 
as  additional  storage;  for,  although  a  part  of  this  may  be 
absorbed  by  vegetation,  the  proportion  will  probably  be  little 
if  any  greater  than  the  loss  by  evaporation  from  the  reservoir. 
Through  a  masonry  dam  there  will  be  a  little  loss,  but  it 
should  be  inappreciable.  Through  an  earthen  embankment, 
however,  the  loss  may  be  considerable.  The  amount  so  lost 
will  depend  upon  the  character  of  this  embankment,  which 
should  be  so  constructed  that  the  daily  seepage  shall  not  be 
more  than  lo  gals,  per  square  foot  of  vertical  longitudinal 
section  of  embankment.  If  the  reservoir  be  ten  times  as  long 
as  the  length  of  the  dam,  and  this  length  be  lOO  times  the 
average  height  of  the  dam,  this  would  give  a  daily  loss  by 
seepage  of  .01  gal.  per  square  foot  of  reservoir  area,  or  3.65 
gals,  per  square  foot  yearly,  or  say  6  inches;  or  about  1.3^ 
of  the  yield.  (These  figures  are  for  New  England  only.) 
With  good  materials  and  workmanship  the  seepage  may  be 
reduced  to  5  or  even  3  gals,  per  vertical  square  foot  of 
embankment. 

Evaporation  and  seepage  combined  may  be  assumed  at 
10^  of  the  consumption  for  the  New  England  and  Central 
Atlantic  States,  which  will  be  a  safe  figure  for  use  when 
accurate  data  are  not  obtainable.  The  consumption  should 
be  increased  or  the  yield  decreased  by  this  percentage,  or  one 
similarly  obtained  in  estimating  storage  and  available  yield. 

For  example,  to  estimate  the  maximum  consumption 
available  from  the  Sudbury  watershed :  we  have  a  mean  yield 
of  30,003,580,000  gals,  per  annum  or  82,200,000  gals,  per 
day.     Allowing  10^  for  loss  as  above,  we  have  27,276,000,000 


S  URFA  CE-  WA  TERS.  1 1  3 

gals,  per  annum  or  74,727,000  gals,  per  day  as  the  maximum 
available  supply. 

A  convenient  method  of  calculating  the  storage  required, 
on  a  given  watershed  of  known  or  assumed  yield,  to  meet 
different  rates  of  consumption,  is  the  graphical  or  "  mass 
diagram  "  one,  the  cumulative  yield  from  the  beginning  of  a 
dry  period  to  the  end  of  each  month  in  succession  being 
plotted  on  the  ordinate  of  that  month.  Such  a  method  is 
shown  in  Plate  VI,  using  a  cycle  of  the  dryest  eleven  years 
on  the  Sudbury  watershed,  viz.,  1878—88.  (See  Fig.  4,  page 
loi.)  The  wavy  line  is  the  curve  of  cumulative  yield,  plotted 
from  the  records.  (From  this  curve  the  greater  yield  in  each 
winter  and  spring  is  very  apparent.)  A  straight  line  FF'  is 
drawn  at  an  angle  representing  30,000,000,000  gals,  per  year 
(the  mean  yield,  also  the  assumed  consumption  plus  loss  by 
evaporation  and  seepage),  and  so  located  as  to  be  tangent  to 
the  curve  and  nowhere  intersecting  it.  The  vertical  distance 
between  FF'  and  the  curve  at  any  point  represents  the 
amount  which  must  be  in  the  storage  reservoir  at  that  time 
if  the  assumed  amount  of  consumption  is  to  be  continuously 
furnished.  Thus  it  appears  that  at  the  beginning  of  this 
eleven-year  cycle  the  reservoir  must  contain  about  37,000,- 
000,000  gals.,  or  more  than  one  year's  consumption;  and 
that  the  capacity  of  the  reservoir  must  be  at  least  56,500,- 
000,000  gals.,  being  full  during  the  spring  of  1879.  After 
this  the  reservoir  becomes  less  and  less  full  until  November 
1885,  when  it  becomes  empty,  but  after  which  time  the  pre- 
cipitation is  sufficient  for  the  consumption.  An  inspection  of 
the  16-year  curve.  Fig.  4,  shows  that  the  supply  required 
in  the  reservoir  on  January  i,  1878,  would  not  have  been 
provided  by  the  yield  of  the  three  previous  years,  but  might 
have  been  accumulating  for  several  years  back. 

If  we  assume  the  reservoir  empty  on  January  i,  1878,  we 
draw  a  straight  line  from  C  tangent  to  the  curve  and  cutting 


114 


yVA  TER-SUPPL  Y  ENGINEERING. 


milI^ons       18"8          ISra         1S80          ISSl         1S82          18 
"'' 'i.*i'-°~5   FAXAO  )FAJAO  IPAJAO  IFAJAODFAJAO   >FAJ 

83         1884         1885         1886          1887         1888             - 
AO  >FAJAO  )FAJAO  )FAJAO  )FAJAO  >FAJAO       j' 

^ .                     t'--" 

ArA  Anyv 

)/        ■^ 

'          ^,             X 

1  '  /   -'     R 

/x  >'      ^^                    i 

j 

/     j/  ^                 t 

/^^^                j^      =                  ::    " 

r        1  j^  •  ^ 

III    1  * '''  -<    <^  1  ''' 

^'^'        / 

c  ''".■,■'    •           ■'     T"     '- 

i          1 

n  -f-               <       , 

' 

,r~ 

__.^__ 

_j    1    1           'I—               ■ 

T1  U  ^'  '  R                   j 

»  h 

Plate  VI. — Yield  and  Storage  Diagram,  Sudbury  Watershed. 


S  URFA  CE-  IV A  TEJiS.  1 1 5 

it  nowhere.  This  line  is  shown  by  CAC,  representing  by 
its  angle  of  slope  24,500,000,000  gals,  annually,  or  about 
67,000,000  gals,  per  day;  less  10^  loss  by  evaporation  and 
seepage  gives  61,000,000  gals,  per  day  available.  We  see  by 
AC  that  this  rate  is  more  than  provided  by  the  yield  after 
January  I,  1884.  We  also  see  that  the  maximum  storage 
required  is  27,000,000,000  gals.,  and  the  reservoir  would  again 
be  full  and  wasting  water  in  April  of  1887  and  all  through 
the  spring  of  1888.  It  is  of  course  not  advisable  ever  to 
permit  the  reservoir  to  become  entirely  empty,  and  a  storage 
of  at  least  30,000,000,000  gals,  should  be  provided  in  this 
case;   and  double  this  amount  in  the  former  one. 

If  but  10,000,000,000  gals,  storage  is  provided,  what  will 
be  the  maximum  uniform  rate  of  consumption  made  possible  ? 
Place  one  end  of  a  thread  at  the  deepest  loop  in  the  curve, 
A,  and  swing  it  towards  the  left  until  the  greatest  vertical 
distance  between  the  thread  and  any  point  of  the  curve  above 
it  is  10,000,000,000  gals. — as  the  line  AB.  As  a  check,  con- 
tinue this  line  towards  the  right  end  of  the  curve,  making 
BAB'  a  straight  line.  No  part  of  AB'  should  come  above 
the  right  half  of  the  curve;  and  if  it  does,  either y^  is  not  at 
the  period  of  greatest  drought,  or  the  storage  is  unnecessarily 
large.  The  rate  represented  by  AB  is  about  17,600,000,000 
gals,  per  year,  or  a  consumption  of  43,800,000  gals,  per 
day. 

This  curve  may  also  be  used  for  finding  the  total,  and 
mean  rate  of,  yield  for  any  length  of  time.  Thus,  from 
March  187?  {E)  to  December  1882  {D),  inclusive,  the  total 
yield  was  138,700 —  14,700,  or  124,000,000,000  gals.;  and 
the  mean  rate,  represented  by  the  angle  of  the  line  DE,  was 
25,700,000,000  gals,  per  annum. 

This  method  is  sufificiently  accurate  for  all  practical  pur- 
poses, except  that  allowance  is  not  made  for  the  variations  in 
monthly   consumption    and    evaporation.      An    approximate 


ii6 


WA  TEK-SUPPL  V  ENGINEERING. 


determination  may,  however,  be  made  by  diagram,  and  more 
accurate  figures  obtained  by  calculation,  as  follows: 

Taking  the  case  of  a  reservoir  with  10,000,000,000  gals, 
capacity,  we  see  that  the  first  storage  begins  in  the  middle 
of  January  1882,  and  we  may  begin  our  table  there.  Quan- 
tities are  in  millions  of  gallons. 


Month. 


Amount 

of 

Yield, 

Mil.  Gals. 


January,     1882 

February  

March 

April 

May 

June 

July 

August 

September.  . . . 

October 

November  . . . . 
December  . .  .  . 
January,  1883. 

February 

March 

April 

May 

June 

July 

August 

September  . . . 

October 

November. .  .  . 
December  . . . . 
January,  1884. 
February  .... 

March 

April 


1446 

5060 

6618 

1957 

301 1 

1193 

201 

129 

691 

697 

472 

733 

780 

2174 

3755 

3044 

2185 

676 

268 

1S3 

205 

433 
461 

451 
2319 
6197 

8824 
6437 


Consump- 

tion and 

Loss. 

607.3 

1257 

7 

1239 

3 

1324 

9 

1483 

6 

1748 

0 

1844 

2 

174S 

0 

1631 

9 

1477 

3 

1350 

3 

1299 

5 

1214 

7 

1257 

7 

1239 

3 

1324 

9 

1483 

6 

1748 

0 

1844 

2 

174B 

0 

1631 

9 

1477 

3 

1350 

3 

1299 

5 

1214 

7 

1257 

7 

1239 

3 

1324 

9 

Surplus 

added 

to 

Reservoir. 


838.7 
3802.3 

5378.7 
632.  I 

1527-4 


916.7 

2515.7 

1719.6 

701.7 


Deficiency 
supplied 

from 
Reservoir. 


II05.2 
4939.6 
7585-0 
5112.4 


555-0 
1643.2 
1619.0 
940.9 
779.6 
87S.0 

565.9 
434.2 


1071 .1 

1575.3 
1564.9 
1426.0 
1044. I 
888.6 
848.4 


Amount 

in 

Reservoir 

at  End  of 

Month. 


838.7 
4641.0 
IOOI9.7 
ICOOO 

1 0000 

9445.0 
7801.8 
6182.3 
5241-9 
4462.3 
3584-3 

3018.4 

25842 
3500.9 

6016.6 
7736.2 

8437-9 
7366.8 

5791-5 

4226.6 
2800.6 

1756.5 
867.9 

19-5 
II24.7 
6064.3 


The  monthly  yield  in  this  was  taken  from  the  record 
(Trans.  Am.  Soc.  C.  E.,  vol.  XXVII.  p.  276);  the  con- 
sumption is  found  by  dividing  17,600  million  gallons  by  i.io 
(10^  for  loss  from  reservoir),  and  the  quotient  by  12  for  the 
monthly  mean  consumption;  the  rate  for  each  month  being 
the  product  of  this  by  the  percentage  given  in  Table  No.  6, 


SURF  A  CE-  IV A  J  EKS. 


117 


page  38.  The  loss  by  percolation  is  taken  as  i^^  of  the 
mean  consumption.  And  the  evaporation  is  found  by  multi- 
plying 8^^  of  the  mean  consumption  by  the  factors  in  Table 
No.  29,  page  91  ;  the  sum  of  these  losses  and  the  consump- 
tion being  given  in  the  third  column. 

It  is  seen  that  by  December  31,  1883,  the  reserve  is 
reduced  to  19.5  million  gallons,  but  is  quickly  brought  up  to 
the  limit  of  the  reservoir  by  the  spring  run-off. 

Another  method  of  making  this  calculation  is  to  correct 
the  monthly  yield  of  the  watershed  for  the  greater  or  less 
yield  of  the  ponds  or  other  water-surfaces  thereon,  including 
the  reservoir,  and  to  consider  only  the  consumption  as  being 
deducted  from  the  reservoir.  For  this  purpose  the  area  of 
water-surfaces  relative  to  that  of  the  entire  watershed  must 
be  known,  and  also  the  yield  of  land-surfaces.  (See  Art.  31, 
page  98.)  To  the  land-surface  yield  over  the  entire  area 
(assuming  seepage  from  ponds  to  contribute  as  much  as 
percolation  from  rainfall  on  an  equal  area)  is  added  the  net 
yield  or  loss  of  each  month  from  the  water-areas. 

The  ponds  and  other  bodies  of  water  on  the  drainage  area 
:;vaporate  more  water  than  do  the  earth.  In  New  England 
the  monthly  rainfall  minus  monthly  evaporation  on  a  water- 
surface  averages  as  follows,  in  inches  of  depth: 


Jan. 

Feb. 

Mar. 

Apr. 

May. 

June. 

July. 

Aug. 

Sept. 

Oct. 

Nov. 

Dec. 

Year. 

2.79 

2.87 

2.50 

0.31 

-  1.09 

—  2.29 

-  1.91 

—  1 .  10 

-0.79 

I  .og 

..67 

1. 91 

5.96 

It  appears  from  this  that  during  May  to  September  the 
evaporation  from  a  pond  is  greater  than  the  rainfall  upon  it; 
and  that  during  an  average  year  the  excess  of  rain,  or  yield, 
is  about  6  inches  only.  In  some  sections  of  the  country  the 
evaporation  is  ten  times  the  rainfall;  and  at  Yuma,  Ariz.,  it 
is  thirty  times;  but  these  sections  are  limited  in  area. 


Il8  WATER.SUPPLY  ENGINEERING. 


Art.  34.     Quality  of  Surface-waters. 

Fallen  rain,  whether  it  flows  over  the  surface  or  through 
the  ground,  is  changing  its  character  continually.  The  sur- 
face flow  takes  into  solution  and  suspension  mineral  and 
organic  matters.  The  mineral  is  mostly  in  suspension,  in  the 
form  of  sand,  clay,  etc. ;  little  being  dissolved  on  account  of 
the  brief  duration  of  contact.  In  the  ground-water  flow  the 
impurities  are  mostly  mineral  because,  the  water  passing 
slowly  through  the  soil  and  over  and  through  rocks,  time  for 
solution  to  take  place  is  given;  and  because  there  is  little  or 
no  organic  matter  in  the  soil  below  a  depth  of  I2  to  i8  inches. 
There  are  exceptions  to  each  of  these  statements;  water 
flowing  over  an  alkaline  soil  will  dissolve  many  of  the  salts 
present;  and  that  flowing  through  underground  beds  of  phos- 
phate and  fish  deposits  and  of  vegetable  matter  of  prehistoric 
origin  will  often  be  high  in  ammonia  and  organic  matter. 

Surface  flow  may  take  into  suspension  large  amounts  of 
both  mineral  and  organic  matter,  which  it  will  later  deposit 
on  less  steep  surfaces  where  the  velocity  of  flow  is  less. 
Underground  flow,  also,  will  generally  purify  a  water -of  all  or 
most  matters  in  suspension,  and  often  of  some  of  those  in 
solution. 

With  the  exception  of  common  salt  and  other  alkaline 
salts,  iron,  and  occasionally  sulphur  and  alum,  water  seldom 
contains  in  solution  sufficient  of  any  mineral  to  make  it 
injurious  or  unpleasant  to  the  taste.  Ground-waters  in  par- 
ticular, however,  frequently  contain  in  abundance  mineral 
matters  which  form  a  food  for  algae  and  other  vegetable 
organisms,  which  latter  attain  such  numbers  as  to  become 
obnoxious  if  not  injurious. 

The  organic  matter  present  is  injurious  when  in  a  putres- 
cent condition.      In  some  cases,  such  as  of  water  from  pe&ty 


S  UK  FA  L  E-  WA  TERS.  1 1 9 

land,  an  objectionable  color  may  be  given  by  the  vegetable 
matter  although  the  water  may  have  no  injurious  properties. 

The  most  dangerous  impurities  are  those  due  to  patho- 
genic bacteria,  which  are  ordinarily,  if  not  invariably,  derived 
from  human  excreta;  and  a  watershed  should  be  carefully 
examined  for  and  guarded  against  such  contamination.  No 
surface  privies  or  overflowing  cesspools  should  be  permitted. 
Deep,  tight  cesspools  at  a  distance  from  any  stream,  and 
from  any  well  (since  the  health  of  occupants  of  the  watershed 
is  very  important  to  the  consumers),  should  be  compulsory 
for  any  scattered  occupants;  and  the  use  of  night-soil  as 
fertilizer  should  not  be  permitted  within  such  drainage  area. 
If  there  is  a  village  or  any  considerable  congregation  of  houses 
on  the  watershed,  these  should  be  provided  with  sewers,  and 
the  sewage  either  so  treated  that  no  germs  can  reach  the 
reservoir,  or  else  discharged  beyond  the  drainage  area  or 
below  all  impounding  reservoirs.  This  is  very  important, 
since  many  epidemics  of  typhoid  fever  have  been  traced  to 
single  cases  upon  a  watershed.  One  such  epidemic  of  con- 
siderable violence  was  due  to  the  depositing  upon  the  snow 
of  the  excreta  of  a  typhoid  patient,  which  were  washed  into 
the  reservoir  with  the  spring  rains. 

Probably  the  greatest  amount  of  impurity  is  found  in 
surface-water  in  the  spring,  when  that  absorbed  by  snow  from 
the  air  and  ground  (which  absorption  is  continued  while  the 
snow  lies)  is  added  to  that  of  the  rainfall,  and  all  passes  over 
the  frozen  ground  without  any  of  the  purification  effected 
by  underground  flow. 

Surface  water,  when  stored  in  reservoirs,  is  subject  to 
certain  changes,  most  of  them  advantageous  but  some  other- 
wise. Much  of  the  matter  in  suspension  is  here  deposited, 
if  the  reservoir  be  of  such  size  that  there  are  no  perceptible 
currents.  Together  with  the  coarser  matter  many  bacteria 
may  be  carried  down,  probably  not  entirely  on  account  of 


I20  WATER-SUPPLY  ENGINEERING. 

their  weight,  but  also  because  their  food-matter  is  settling  to 
the  bottom.  At  Oberlin,  O.,  for  example,  the  number  of 
bacteria  was  found  to  be  reduced  from  2000  per  cubic  centi- 
meter in  a  15,000,000-gallon  reservoir  to  426  in  the  effluent. 
In  the  Chestnut  Hill  Reservoir  (Boston)  in  1894  the  average 
number  of  bacteria  found  at  the  surface,  middle,  and  bottom 
were  y'/,  246,  and  319  respectively;  the  surface-water  at  no 
time  containing  more  than  one  half  the  number  found  at  the 
bottom.  The  benefit  of  sedimentation  to  a  water-supply  is 
illustrated  by  the  typhoid-fever  epidemics  at  Philadelphia  in 
1 89 1  to  1899,  where  the  highest  mortality  was  almost  in- 
variably found  where  water  was  pumped  directly  to  the 
consumers,  and  the  lowest  where  the  capacity  of  the  reservoir 
relative  to  the  consumption  was  greatest. 

Waters  entering  a  reservoir  from  soils  of  different  charac- 
ter, and  as  both  surface-  and  ground-flow,  will  possess  different 
characteristics.  These  waters  largely  intermingle,  the  more 
polluted  being  diluted  by  the  purer,  and  to  a  certain  degree 
chemical  combinations  resulting.  For  instance,  the  ammonia 
of  a  polluted  water  may  be  oxidized  into  nitrates  by  the  free 
oxygen  in  a  purer  water;  or  ferrous  oxide,  by  a  similar  addi- 
tion of  oxygen,  may  become  insoluble  ferric  oxide  and  settle 
to  the  bottom. 

In  addition  to  these  processes  continual  changes  are  being 
effected  by  the  living  organisms  in  the  water,  both  vegetable 
and  animal.  The  former  consume  only  the  mineral  matters 
in  the  water,  both  those  originally  so  and  those  resulting  from 
the  decomposition  of  organic  matter  (except  that  bacteria 
decompose  organic  matter  also);  the  animal  organisms  subsist 
upon  the  organized  matter,  including  other  living  animal  and 
vegetable  organisms.  The  lower  organisms  have  by  far  the 
greater  power  of  multiplication,  and  may  increase  more 
rapidly  than  the  higher  organisms  for  which  they  serve  as 
food,  and  their  death  and  decomposition  result  in  a  pollution 


S  URFA  CE-  WA  TERS.  121 

of  the  water.  As  a  familiar  illustration,  a  considerable 
increase  in  mineral  matter  suitable  for  plant-food,  or  in  the 
nitrogen  resulting  from  the  decomposition  of  organic  matter, 
may  suddenly  cause  the  presence  of  vast  numbers  of  algai, 
which,  not  being  accompanied  by  a  similarly  rapid  increase 
in  animal  organisms  which  will  consume  them,  cause  gross 
pollution  of  the  water. 

If  a  reservoir  is  used  without  the  flooded  portion  being 
first  cleaned  of  all  organic  matter — leaves,  bushes,  stumps, 
roots,  etc. — these  furnish  food  for  great  numbers  of  organ- 
isms, but  sufificient  increase  in  the  number  of  higher  animals 
to  keep  the  water  clear  is  prevented  by  natural  limitations 
both  of  propagation  and  of  existence,  especially  by  the  small 
amount  of  oxygen  in  such  w'ater;  and  pollution  thus  caused 
will  continue  for  many  years.  For  this  reason  reservoirs 
should  be  carefully  cleared  before  use,  not  only  of  the  surface 
vegetation,  but  of  the  vegetable  soil-matter  or  humus  also. 
An  investigation  made  by  the  city  of  Boston  of  the  site  of 
the  Nashua  reservoir  indicated  that  below  a  depth  of  9  to  12 
inches  there  was  little  organic  matter — in  few  cases  more  than 
2^,  but  above  this  the  amount  was  considerable;  and  conse- 
quently the  top  soil  was  removed  to  this  depth  at  a  cost  of 
about  $3,000,000.  In  cases  where  the  expense  of  this  seems 
prohibitive  the  reservoir  should  at  least  be  thoroughly  cleared 
of  all  vegetation,  and  all  stumps  and  roots  grubbed  out. 
Clean  sand  or  gravel  spread  over  the  soil  forms  an  excellent 
and  sightly  bottom  for  a  reservoir,  and  will  to  some  extent 
prevent  the  evil  effects  due  to  organic  top-soil;  but  the 
removal  of  all  organic  matter  is  decidedly  preferable. 

While  w^ater  stands  in  a  reservoir  the  top  surface  becomes 
heated  in  summer  and  cooled  in  winter  more  than  do  the 
lower  strata.  Wind  stirs  the  water  to  a  depth  of  5  to  20 
feet,  and  causes  it  to  be  warmed  somewhat  to  this  depth  in 
summer,  although  the  warmer  water,  being  lighter  than  the 


122 


WATER-SUPPLY  ENGINEERING. 


cold,  remains  always  near  the  top.  In  winter  the  cooler 
surface-water  settles  to  the  bottom,  and  the  temperature  thus 
becomes  more  nearly  uniform,  the  bottom  being  generally 
somewhat  warmer. 

The  following  table  gives  the  average  temperature  of  the 
surface  of  several  ponds  and  reservoirs  in  Massachusetts,  and 
of  the  air  at  the  same  time,  by  months. 

Table  No.  37. 

TEMPERATURE     OF     PONDS    AND     RESERVOIRS    IN     MASSACHUSETTS 
(degrees    FAHR.). 


Jan. 

Feb. 

Mar. 

Apr. 

May. 

June. 

July. 

Aug. 

Sept. 

Oct. 

Nov. 

Dec. 

Surface  of 
water. . . . 
Air 

.( 

35-3 

24- I 

35-3 
25.8 

36.7 
32.2 

44-3 
43-9 

57-7 
56.3 

67.9 
66.0 

73-7 
71.4 

72.9 
68.6 

66.9 
60.8 

55-2 
so.  I 

44.1 
39.0 

36.1 
28. 5 

The  higher  temperature  of  the  water  is  due  to  the  sun 
(the  air  temperature  being  taken  in  the  shade)  and  the  longer 
retention  of  heat  by  water  than  by  air.  There  were  few 
variations  from  these  average  temperatures  of  more  than 
1°  to  5°,  the  shallow  ponds  being  generally  the  warmer. 

Table  No.  38  gives  the  temperature  of  Jamaica  Pond 
(Boston)  and  Lake  Cochituate  at  different  depths,  showing 
the  variations  referred  to  above. 

Table  No.  38. 

temperature  of  lakes  at  different  depths. 
(Mass.  State  Bd.  of  Health.) 

Jamaica  Pond,  July  14,  1891. 


Depth 

Temperature  of  Water 

Percentage  of  Dissolved  Oxygen. 


Surface. 

10' 

20' 

30' 

35' 

,      i 
40' 

75-4 

75 

54 

424 

42. 

42 

100 
(Saturi 

100 
ited). 

49 

39-47 

4.18 

0 

47' 
41-3 


Lake  Cochituate,  August  17,  1891. 


Depth 

Temperature  of  Water 

Percentage  of  Dissolved  Oxygen. 


Surface. 

10' 

20' 

30' 

40'         45' 

so' 

74-7 

66.4 

S3. 6 

49-3 

48.2      48.2 

45-7 

79-»5 

83.69 

35.86 

21-33 

20.93       1-65 

0 

57 
44-8 


SURF  A  Ch-  WA  TERS. 


123 


In  summer  the  only  motion  in  the  water  of  lakes  and 
reservoirs,  aside  from  an  inappreciable  current,  is  that  due  to 
the  wind.  If  the  bodies  of  water  are  large  and  exposed  this 
agitation  may  extend  to  a  depth  of  10  or  even  20  feet,  where 
the  water  attains  this  depth;  but  if  the  body  of  water  be 
small  or  shut  in  by  woods  there  may  be  little  of  such  effect 
felt.  It  is  found  that  all  water  below  that  which  is  so  stirred 
up  forms  a  comparatively  stagnant  layer.  Since  much  of  the 
organic  matter  in  the  water  settles  to  the  bottom,  this  often 
becomes  very  foul  and  all  of  the  free  oxygen  here  is  utilized 
in  nitrifying  such  matter.  In  Table  No.  38  this  is  illustrated 
by  data  from  two  reservoirs;  the  upper  10  or  15  feet  being 
stirred  up  by  wind  continually  absorbs  fresh  oxygen,  while 
retaining  little  organic  matter  to  consume  it;  but  the  bottom 
15  or  20  feet,  containing  much  organic  matter,  is  very  low  in 
oxygen.  This  fact  is  also  illustrated  in  Table  No.  39,  by  the 
difference  in  amount  of  organic  matter,  as  represented  by  free 
ammonia,  in  the  surface  and  bottom  waters  of  several  reser- 
voirs and  lakes. 

Table  No.  39. 

DEPOSITS    OF     ORGANIC     MATTER,    AS    FREE    AMMONIA,    AT    THE    SUR- 
FACE   AND    BOTTOM    OF    DIFFERENT    BODIES    OF    WATER. 


Date. 

Depth 

of 
Water. 

Depth  of 
Deepest 
Sample. 

Free  Ammonia. 

Surface. 

Near 
Bottom. 

Jamaica  Pond,  Mass 

Aug.   14,  1890 
Aug.   27.  1889 
Sept.   18,  1890 
July    24,  1889 
Aug.   31,  1887 
Aug.   28,  1893 

57 
36 
65 
46 
46 

50 
35 
60 

45 

40 

1 10 

O.OOOO 
0.0012 
0 . 0004 
0 . 0000 
0 . 0000 
0.0000 

0.4720 

0. 1760 
O.06S0 
0.0560 
0.0021 
0.0000 

Lake  Cochituate,  Mass 

Wcnham  Lake,  Mass 

Boston  Reservoir  No.  4  .  . . . 
Lake  Winnepesaukee,  N.  H, 

This  table  also  shows,  by  the  last  two  illustrations,  that 
the  stagnant  layer  is  not  necessarily  foul,  but  only  when 
organic  matter  is  present  in  the  water. 


1 24  }VA  TER  SUP  PL  V  ENGINEERING. 

"  As  the  surface-water  cools  in  the  autumn  and  becomes 
heavier  than  the  water  below  the  surface,  vertical  currents  are 
produced  which  extend  down  to  and  somewhat  beyond  the 
depth  where  the  water  is  at  the  same  temperature  as  at  the 
surface.  These  currents  are  nearly  continuous  and  extend 
deeper  and  deeper  as  the  season  advances,  until  some  time  in 
November,  when  they  extend  to  the  bottom  of  the  pond. 
After  they  have  reached  the  bottom  they  continue  to  keep 
the  water  in  motion  for  several  weeks  until  the  whole  of  the 
water  in  the  pond  has  reached  the  temperature  of  maximum 
density."  "In  a  lake  with  any  considerable  amount  of 
organic  matter  in  it  and  also  in  deep  artificial  storage-reser- 
voirs, where  the  surface  has  not  been  stripped,  the  lower 
layers,  which  are  quiescent  during  the  stagnation  period, 
gradually  collect  all  the  organic  matter  from  the  upper  layers, 
and  decay  goes  on  until  the  oxygen  is  used  up.  The  water 
becomes  darker  and  darker,  until  by  October  it  is  very  yellow, 
and  generally  has  a  disagreeable  smell.  Of  course,  when  the 
great  overturning  comes,  in  November,  all  this  bad  water  is 
brought  to  the  surface,  and  the  infusoria  and  diatoms  begin 
to  grow  in  enormous  numbers,  because  the  organic  matter 
and  oxygen  are  brought  together  and  provide  food  for 
organic  life.  The  same  phenomenon  takes  place  in  the  spring 
period  of  circulation,  although  on  a  smaller  scale."  (Fitz- 
Gerald  on  the  "  Temperature  of  Lakes,"  Trans.  Am.  Soc.  C. 
E.,  vol.  XXXIV.) 

In  Plate  VII  are  shown  the  typical  winter  and  summer 
temperatures  of  a  lake  that  freezes. 

The  above  explains  the  sudden  presence  in  water-supplies 
of  the  "  fishy  "  taste  which  is  so  unpleasant,  it  being  caused 
by  some  matter — probably  an  oil — given  up  by  the  decom- 
position of  many  species  of  algc-E. 

If  the  water-supply  be  drawn  from  the  surface  of  a  reser- 
voir from  May  to  September,  the  purest  water  will  thus  be 


SUI^FA  CE-  WA  TERS. 


125 


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126  WATER-SUPPLY  ENGINEERING. 

obtained.  If  now,  just  before  the  overturn,  the  bottom 
layer  of  impure  water  be  drawn  off  through  a  waste-pipe, 
much  of  the  fouling  of  the  reservoir  will  be  avoided.  If 
neither  the  water  nor  the  bottom  of  the  lake  or  reservoir 
contain  organic  matter  or  nitrogen,  all  this  trouble  is  of  course 
avoided. 

If  much  unoxidized  organic  matter  remain  in  a  reservoir 
when  this  is  frozen  over,  and  the  access  of  additional  oxygen 
to  the  water  from  the  air  is  thus  shut  off,  putrefaction  may 
take  place  with  its  resulting  gases;  but  this  can  happen  only 
when  the  water  is  more  impure  than  any  supply  should  be. 

Ice  is  not  an  important  source  of  supply  in  this  country, 
although  it  is  in  some  extreme  northern  ones,  and  in  certain 
localities  in  the  Alps.  A  comparatively  small  amount  is 
used  in  ice-water,  however,  and  for  this  reason  its  purity  is 
of  importance.  Impure  ice  is  as  dangerous  as  impure  water; 
and  the  popular  idea  that  water  is  purified  in  freezing  is 
but  partially  true,  much  of  both  organic  and  inorganic 
impurity  frequently  remaining  in  the  ice.  When  water  is 
frozen  slowly,  however,  much  of  the  impurity  is  excluded  and 
is  taken  up  by  the  remaining  water,  which  thus  becomes  more 
impure.  Hence  the  most  impure  ice  is  that  frozen  last,  and 
is  generally  found  at  the  bottom,  if  from  a  shallow  pond,  or  at 
the  centre  of  artificially  frozen  cakes.  From  deep  ponds, 
however,  the  under  side  of  the  ice  is  purest,  because  the  slight 
increase  in  impurity  of  the  lower  water  caused  by  the  freezing 
of  the  surface  is  more  than  offset  by  the  greater  percentage  of 
purification  effected  by  the  slower  freezing  of  the  under  ice. 
When  ice  is  flooded,  all  the  impurities  in  the  flooding  water 
must  be  contained  in  the  ice.  This  refers  to  bacteria  as  well 
as  to  other  impurities. 

"It  is  generally  unsafe  to  use  ice  from  a  polluted  source," 
but  apparently  pure  ice  maybe  obtained  "  by  removing  from 


A  L'KFA  CE-  WA  TERS. 


127 


the  ice  when  harvested  the  first  inch  that  formed  upon  the 
pond  and  all  of  the  ice  which  may  have  formed  above  the  first 
inch  from  snow,  rain,  or  flooding."  (Rep't  Mass,  State  B'd 
of  Health,  1900.) 

The  following  data  (selected  from  Mason's  "Sanitary 
Water-supply")  show  the  amount  of  purification  by  freezing 
in  several  instances. 


Troy  City  supply 

Ice  from  same 

Very  hard  spring  water 

Ice  from  same 

Water  from  Erie  Canal  where 

public  ice  supply  is  taken.  . 
Ice  from  above  locality,  used 

for  public  supply 


Total 
Residue 

from 
100  c.c. 


.0092 
.0010 
.0540 
.0045 

.0112 

.0067 


Loss  on 

Itfnition, 
Volatile 

and 
Organic 
Matter. 

Inorganic 
Residue. 

•0035 

.0057 

.0010 

trace 

.00 

.0540 

.00 

.0045 

.0033 

.0079 

.0025 

.0042 

Per  cent  of 
the  Miner- 
al Matter 
originally 

in  the 
water,  yet 
remaining 
in  the  ice. 


8.3 


53-2 


Per  cent  of 
Organic 
and  Vola- 
tile Mait^r 

of  the 
water,  yet 
remaining 
in  the  ice. 


28.5 


75-7 


Dr.  Prudden  found  in  ice  which  had  been  frozen  for  eleven 
days  1,019,403  bacteria  per  cubic  centimeter;  in  that  frozen 
seventy-seven  days,  72,930;  and  in  that  frozen  one  hundred 
and  three  days,  7348  per  cubic  centimeter.  He  also  found 
from  50  to  200  times  as  many  bacteria  in  snow-  or  bubbly-ice 
as  in  clear,  transparent  ice  free  from  air. 

QUERIES. 

9.  The  Sweetwater  reservoir  has  an  area  of  530  acres  when  half 
full.  Assuming  this  area  as  an  average,  correct  the  calculation  in  Art. 
II  for  evaporation  from  this,  and  find  the  area  that  can  be  irrigated. 

10.  If  the  Sudbury  basin  contain  2^  of  water-surfaces  on  its 
area,  find  the  yield  in  1883  of  a  neighboring  watershed  similar  in 
all  respects  except  that  zoic  of  its  area  was  water-surfaces. 

11.  How  account  for  the  percentage  yielded  being  greater  than 
100  during  certain  months,  as  given  in  Table  2,Zy  P^ge  99  ?  Why  is 
the  May  percentage  lower  and  the  fall  percentage  higher  in  the 
Potomac  than  in  the  Connecticut  River  basin  ? 


CHAPTER  VII. 

RIVERS   AND    LAKES. 

Art.  35.     Rivers. 

Surface-water  is  generally  collected  as  well  up  towards 
the  head  of  a  stream  as  possible,  both  because  the  greatest 
fall  is  thus  obtained  to  the  point  of  utilization,  and  because 
here  are  more  frequently  found  the  best  locations  for  reser- 
voirs and  dams.  This  source  of  supply  is  most  applicable  to 
hilly  or  mountainous  country,  whose  watersheds  are  sparsely 
occupied, — conditions  generally  associated  with  a  poor  and 
thin  soil. 

In  the  lower  lands  there  are  few  locations  for  reservoirs, 
and  pumping  must  generally  be  resorted  to;  moreover  the 
streams  here  are  usually  of  sufficient  size  to  furnish  an  ample 
supply  even  in  dry  times.  The  water  is  therefore  taken 
directly  from  the  stream,  and  no  storage  is  required,  although 
it  may  be  desirable  for  permitting  sedimentation. 

The  quantity  of  water  flowing  in  a  river  is  that  reaching 
it  by  surface  or  underground  flow  from  all  the  drainage  areas 
above  on  all  its  branches,  less  what  may  have  been  removed 
by  evaporation,  by  seepage,  and  by  man  for  irrigation  and 
other  purposes.  A  part  of  the  flow  may  in  some  cases  be 
underground,  beneath  and  near  the  bed  of  the  river. 

The  yield  to  the  river  will  be  the  total  yield  of  the 
drainage  areas  of  all  its  tributaries,  the  estimating  of  which 
has  already  been  discussed  under  the  head  of  surface-water, 

128 


EJVEKS   AND    LAKES.  1 29 

The  evaporation  will  be  that  from  its  entire  surface  and  from 
the  surfaces  of  all  tributary  streams,  ponds,  lakes,  and  other 
bodies  of  water.  (For  the  rates  see  Tables  Nos.  27,  28,  and 
29.)  The  seepage  will  vary  from  almost  nothing  to  the 
entire  volume  of  flow,  depending  upon  the  character  of  soil, 
amount  and  character  of  sediment  carried  by  the  stream,  and 
height  of  ground-water.  In  a  clay  or  rock  channel  the 
seepage  will  be  very  small.  In  a  sandy  soil  it  may  be  great; 
but  if  loamy  or  clayey  matter  is  carried  to  the  stream  by  heavy 
rains,  this  will  gradually  be  deposited  as  sediment  upon  the 
bottom  and  form  an  impervious  channel. 

If  the  ground-water  stands  level  with  or  above  the  river- 
surface,  there  will  be  no  loss  by  seepage,  but  rather  a  gain. 
Such  ground-water,  however,  must  be  derived  from  the 
drainage  area  of  the  stream,  and  hence  be  included  in  the 
general  calculation  of  yield.  This  ground-water  will  usually 
flow  slowly  both  towards  the  river  and  down  its  valley. 

In  many  Western  rivers  the  flow  is  in  places  altogether 
beneath  the  surface  during  a  large  part  of  the  year,  the  river- 
bed being  dry  except  during  rainy  seasons.  At  certain  points 
in  the  courses  of  many  of  these  rivers  rock  or  clay  outcrops 
through  the  porous  soil,  and  here  the  water  is  forced  to  the 
surface  and  flows  in  the  channel,  to  disappear  again  further 
on  where  the  impervious  stratum  again  dips  beneath  the  sur- 
face. Several  of  these  rivers  have  no  visible  outlet,  .but 
simply  disappear  into  the  ground,  from  which  the  water  is 
absorbed  by  vegetation  and  evaporated. 

A  few  rivers  flow  for  a  part  of  their  course  through  under- 
ground caverns,  generally  in  the  limestone;  but  these  are  so 
exceptional  as  to  require  no  special  consideration. 

The  underground  flow  of  a  river  can  either  be  utilized  as 
ground-water  (see  Chapter  VIII),  or  in  some  cases  can  be 
intercepted  by  a  dam  carried  down  to  the  impervious  stratum 
and   across   the   channel    of    pervious    soil    which    affords    it 


130  WATER-SUPPLY  ENGINEERING. 

passage.  Such  a  dam,  which  causes  the  porous  soil  above  to 
act  as  a  storage-reservoir,  has  been  built  across  Pacoima 
Creek,  Cal.,  the  channel  in  bed-rock  being  at  this  place  but 
550  feet  wide  and  filled  with  gravel  to  a  depth  of  40  feet. 

An  estimate  of  the  quantity  of  water  flowing  in  a  river  at 
various  seasons  can  be  made  by  deducting  from  the  rainfall 
the  evaporation,  both  from  earth  (including  plant-consump- 
tion) and  from  water-surfaces;  01  by  other  methods  of 
estimating  yield  referred  to  in  Art.  31.  But  the  only  accu- 
rate method  is  by  direct  measurement,  and  this  is  of  greater 
value  the  longer  the  series  of  years  it  covers.  Variations  in 
river-flow  are  illustrated  in  Tables  Nos.  34  and  35,  pages  100 
and  102,  and  it  is  here  seen  that  the  maximum  may  be  500 
times  the  minimum,  and  the  latter  but  5  to  10  per  cent  of 
the  mean  annual  flow.  If  this  minimum  amount  is  not  more 
than  the  consumption,  an  additional  source  must  be  obtained; 
or  means  provided  for  storing  the  river-water,  either  by  dam 
in  the  river  itself,  or  by  a  storage-reservoir  into  which  the 
water  is  pumped.  The  latter  is  generally  preferable,  but 
frequently  the  more  expensive  of  the  two. 

Art.  36.     Quality  of  River-water. 

The  quality  of  rain-water  when  it  reaches  a  stream  has 
already  been  considered,  but  there  are  many  changes  in  it 
continually  taking  place  after  this.  As  in  the  case  of  reser- 
voirs, mineral  and  other  impurities  carried  in  suspension  are 
deposited  as  the  current  velocity  becomes  less,  but  more 
slowly  in  rivers  because  of  the  greater  motion  in  the  water. 
The  stratification  found  in  reservoirs  and  lakes  does  not  exist 
in  rivers,  the  current  keeping  the  water  in  constant  circula- 
tion. For  the  same  reason  the  temperature  of  rivers  is  more 
uniform  at  different  depths,  although  varying  more  from 
month  to  month;  the  variation  being  between  32°  and  80°  in 


mVEJiS  A  AD    LAKES.  I3I 

seven  Massachusetts  rivers.  Also  more  oxygen  is  generally 
available  for  nitrification  in  a  river  than  in  a  lake  or  reservoir, 
since  all  parts  of  the  water  are  in  turn  brought  in  contact  with 
the  air. 

In  spite  of  these  means  of  purification,  however,  the 
water  of  a  river  is  generally  less  pure  than  that  of  the  run-off 
contributing  to  it,  owing  to  the  impurities  reaching  it  from 
the  various  farms  and  communities  past  which  it  flows.  The 
most  dangerous  of  these  is  sewage  contamination,  although 
that  from  slaughter-houses  and  rendering  establishments  is 
fully  as  offensive  and  is  far  from  being  harmless.  Waste 
waters  from  dye-works  and  numerous  other  manufacturing 
industries  may  render  a  water  totally  unfit  to  drink.  A 
minor  source  of  impurity,  although  it  may  become  an  im- 
portant one,  is  the  waste  from  passenger-steamers  and  other 
boats. 

Since  each  person  excretes  every  day  an  average  of  .015 
lbs.  of  free  ammonia,  .003  of  albuminoid  ammonia,  .218  of 
solids,  and  .042  lbs.  of  chlorine,  the  pollution  added  by  the 
sewage  of  a  large  community  is  seen  to  be  considerable;  but 
more  serious  still  are  the  bacteria,  millions  of  which  are  found 
in  each  thimbleful  of  sewage,  and  some  of  which  may  at  any 
time  be  pathogenic. 

The  pollution  from  manufacturing  establishments  may 
consist  of  almost  any  acids,  alkalis,  or  organic  matters.  A 
carpet,  blanket,  and  cloth  mill  on  the  Schuylkill  River  used 
daily,  a  few  years  ago,  48,700  lbs.  of  organic  matter  in  18 
different  forms;  2520  lbs.  of  21  different  acids;  and  950  lbs. 
of  6  different  alkalis.  Brass-w^orks  discharge  considerable 
sulphate  of  copper,  cyanide  of  potash,  and  oils.  The  prin- 
cipal waste  from  iron-works  is  sulphate  of  iron;  from  paper- 
mills  come  filaments  of  jute,  cotton,  and  other  organic 
matters,  caustic  soda,  chloride  of  lime  and  sulphite;  from 
woollen-factories    the    washing    of    the  wool  produces  large 


132 


WATER-SUPPLY  ENGINEERING. 


amounts  of  organic  wastes,  and  soda,  alkalis,  logwood, 
fustic,  madder,  copperas,  potash,  alum,  blue  vitriol,  muriate 
of  tin,  and  other  dye-wastes  are  found  in  the  waste-waters. 
This  list  might  be  continued  indefinitely;  but  the  appearance 
of  most  rivers  receiving  such  wastes  is  evidence  of  the  serious- 
ness of  the  contamination. 

The  following  table  gives  an  analysis  of  the  Passaic  River, 
showing  gross  pollution  due  partly  to  manufacturing  wastes, 
but  even  more  to  sewage  pollution;  and  also  an  analysis  of 
the  relatively  pure  Hudson,  although  this  receives  the  sewage 
of  several  cities  and  towns  above  Albany. 

Table  No.  40. 

ANALYSIS    OF    PASSAIC    AND     HUDSON    RIVER    WATER. 


c 

^ 

u 

Ammonia. 

Nitrogen  as 

0 

V 

u 

in 

'c 

be 

ii 

u 

a 

c 

u? 

0 

*—* 

c'^ 

a 

"  .   >•■■> 

V 

B 
3 

rt 

u 

in 

0 

0 

c 

u 
u 

i 

h 

< 

u 

2; 

Z 

H 

►J 

i 

^ 

m 

Passaic,     below     Passaic 

Falls 

.02947 

.04220 

.8116 

.0542 

.00296 

10.856 

3.a3> 

7.025 

•  5694 

747,000 

Hudson,  above  Albany. . 

.0030 

.0087 

•  35 

trace 

.000 

7-3 

3-5 

3.« 

.37& 

Although  there  is  considerable  movement  of  river-water, 
both  vertically  and  across  the  stream,  still  the  greatef  part 
of  the  suspended  material  transported,  together  with  the 
bacteria,  is  found  near  the  bottom;  also  an  impure  stream 
entering  on  one  side  of  a  river  may  travel  for  miles  before 
being  equally  commingled  with  the  purer  water.  These  facts 
should  be  taken  advantage  of  in  locating  an  intake. 

A  great  objection  to  many  river-waters  is  the  large  amount 
of  mineral  matter  in  suspension  carried  in  time  of  flood. 
The  use  of  turbid  water  is  in  some  cases  avoided  by  providing 
storage-reservoirs  holding  sufficient  clear  water  to  permit  the 
discontinuance  of  pumping  when  the  river  is  muddiest.  This 
is  always  after  a  rain,  and  may  last  for  but  a  day  or  two  at  a 


RIVERS   AND   LAKES. 


133 


time;  the  duration  varying  directly  with  the  size  of  the 
drainage  area  above.  The  extreme  variation  in  the  amount 
of  silt  present  in  some  rivers  is  illustrated  by  the  Ohio,  in 
which,  in  1895,  the  maximum  amount  of  suspended  matter 
found  was  531.1  parts  per  100,000,  the  minimum  was  o.  i 
part,  and  the  mean  22.5  parts. 

It  is  probable  that  manufacturing  wastes  and  sewage  are 
in  most  cases  quite  constant  in  amount,  and  hence  the 
polluted  water  is  most  impure  when  the  river  is  low.  The 
quantity  of  organic  matter  washed  from  the  banks,  which 
may  include  considerable  human  excreta,  will  be  greatest 
after  a  rain.  There  will  in  most  rivers  be  a  wide  variation 
and  sudden  changes  in  the  impurities  found,  both  mineral  and 
organic.  Table  No.  41  shows  such  variation  for  the  Hudson 
River  above  any  direct  sewage-inflow. 


Table   No.   41. 

VARYING     AMOUNTS    OF    IMPURITIES     IN    RIVER    WATER    (mASOn). 
(In  parts  per  1,000,000.) 


Ammonia. 

Nitrogen  as 

u 
c 
u 

0 

U 

K 

0 

•a 
a> 

'5  c 

3 
."2 

0 

H 

c 

0 

'c 
be 

c 
0 

'J-. 

0 

t75 

"is 

0.  a 

vt 

Date. 

T3 

'0 

< 

V 

u 

g 

3  tn 

Q.bfl 

Nov.     3,  1894. . 
Dec.    15,     "    .. 
Jan.    12,  1895. . 
Feb.      5.     "    .. 
Mar.     4,     "    ,. 
April    5,     "    . . 
"     10,     "    .. 
May     8,      "    .. 
June      5,      "     .. 
Sept.  20,      "    , . 

,030 
•045 
.025 

•055 
.085 
.042 
.058 
.030 

.045 
.280 

•055 

.087 
.150 
.080 
.  100 
.150 

•  235 
.660 
.205 
.120 

•  320 

•  155 

.000 

trace 

.000 

.000 

trace 

.000 

.0015 

trace 

trace 

•15 
.10 

•15 
.ro 
•30 

trace 
.10 

trace 
•30 

3-5 
4-5 
3-5 

2.4 

2.5 
3-5 
5-0 
3-5 

3-76 
13.00 

7-65 

8.85 

10.00 

5-90 
15-50 
7-30 
8.70 
2.65 
14.85 

73 
107 

43 

88 

93 

388 

583 

67 

78 

35 
42 

39 
45 
51 

88 

74 
31 
50 

88.4 

68.8 
0.0 
0.0 
0.0 

II. 0 

495.0 

0.0 

0.0 

'36*' 

34-6 

33- 

46.4 

41. 

68. 

71- 

Oct.    30,      "    .. 

lOI 

57        0.0 

44 

The  record  of  April  loth  shows  the  largest  amount  of 
albuminoid  ammonia  coincident  with  that  of  suspended 
matter,  and  hence  probably  caused  by  rain. 


134  WATER-SUPPLY  ENGINEERING. 

The  increase  of  bacteria  caused  by  rain  washing  them  into 
a  stream  is  illustrated  by  the  Croton  (New  York  City)  water, 
which  ordinarily  contains  about  35  bacteria  per  cubic  centi- 
meter, but  after  a  hard  rain  as  many  as  7200  have  been  found. 
River-water  generally  contains  more  bacteria  in  winter  than 
in  summer. 

Art.  37.     Lakes. 

A  lake  is  generally  but  the  broadening  of  the  channel  of 
a  river  or  other  stream,  and  the  water  entering  a  lake  is  but 
that  of  such  stream.  The  quantity  of  water  passing  through 
a  lake  is  no  more  than  that  flowing  in  its  river;  but  when  this 
latter  becomes  temporarily  small  in  times  of  drought  the  lake 
acts  as  a  storage-reservoir,  and  hence  is  generally  preferable 
to  a  river  as  a  source  of  supply,  if  the  quality  is  equally  as 
good. 

In  passing  through  a  lake  water  often  undergoes  changes 
in  quality  which  would  not  occur  in  the  stream.  Lakes  are 
ordinarily  found  in  a  hilly  country,  where  the  currents  of  the 
streams  are  more  or  less  rapid,  while  that  through  the  lake 
is  very  slow.  Suspended  matter  which  was  carried  by  the 
stream  is  therefore  permitted  in  a  lake  to  settle  to  the 
bottom,  and  the  water  is  thus  clarified;  many  bacteria  being 
carried  down  during  the  sedimentation,  or  dying  off  from 
lack  of  food-matter.  The  water  at  the  lower  end  of  a  lake  is 
hence  in  most  cases  purer  than  that  at  the  upper  end,  pro- 
vided no  pollution  finds  its  way  into  the  lake  from  the  shores. 
There  being  no  more  water  flowing  through  a  lake  than  flows 
in  the  river  in  whose  course  it  lies,  there  will  be  in  the  long 
run  no  more  dilution  of  sewage  or  other  impure  water  dis- 
charged into  a  lake  than  if  the  same  were  discharged  into  the 
river;  but  the  water  may  become  more  pure  in  passing  over 
a  given  distance,  because  of  the  greater  time  occupied  and 
the  greater  opportunity  for  sedimentation  thus  afforded. 


KIVERS   AND    LAKES.  135 

Most  lakes  are  deeper  than  their  rivers,  and  such  effect  as 
depth  may  have  upon  the  quahty  of  water  is  found  in  many 
or  most  lakes.  Owing  to  this  depth,  to  the  size  of  a  lake  as 
compared  with  a  river  channel,  and  to  the  slight  current 
movement,  lakes  offer  better  opportunities  for  locating  water- 
works inlets  than  do  rivers  or  smaller  streams. 

Like  river-water,  lake-water  must  ordinarily  be  pumped; 
except  in  the  case  of  lakes  on  mountain  streams,  which  act 
practically  as  natural  reservoirs  of  surface-water.  In  fact, 
lakes  and  reservoirs  have  in  most  respects  similar  effects  upon 
the  quality  of  water;  and  most  of  the  statements  made  in 
Art.  34  concerning  reservoirs  are  applicable  likewise  to  lakes. 

QUERIES. 

12.  If  the  Passaic  were  flowing  looo  cu.  ft.  per  second  when  the 
analysis  in  Table  40  was  made,  how  many  people  were  apparently 
contributing  sewage  to  it,  assuming  that  all  the  free  ammonia  was 
from  sewage  ?  Assuming  the  same  of  albuminoid  ammonia  ?  Of 
chlorine  ? 


CHAPTER  VIII. 

G  R  O  U  N  D-W  A  T  E  R. 

Art.  38.     Water-bearing  Strata. 

The  rainfall  absorbed  by  the  soil  of  each  catchment  area, 
after  percolating  downward,  continues  to  travel  in  some 
generally  horizontal  direction  toward  a  stream,  lake,  or  sea. 
Its  underground  passage  is  subject  to  many  of  the  laws 
affecting  surface-flow — its  surface  must  fall  in  the  direction 
of  flow,  and  the  velocity  of  flow  is  proportional  to  this  fall; 
the  hydraulic  gradient  of  this  flow  cannot  be,  at  any  point, 
lower  than  the  bcdy  of  water  into  which  the  flow  discharges; 
the  water  will  seek  the  lowest  accessible  channels,  but 
ordinarily  fills  the  soil  over  large  areas.  There  are  the  addi- 
tional influences  of  friction  in  passing  through  the  soil;  the 
capillary  attraction  of  this;  and  confined  flow  caused  by 
super-strata  of  impervious  material,  the  conditions  then 
approximating  those  found  in  water-pipes  or  other  conduits 
under  pressure. 

The  amount  of  flow  is  dependent  upon  the  size  and  per- 

viousness  of  the  catchment  areas  which  contribute  to  it,  and 

upon  the  precipitation  upon  those  areas.     It  is  in  many  cases, 

however,    increased    by    seepage    from     rivers    crossing    the 

pervious  stratum,  the  drainage  areas  of  which  rivers  are  not 

strictly  parts  of  the  catchment-basin  in  which  this  pervious 

stratum  lies. 

136 


GRO  UND -  WA  TER.  137 

If  AB  is  a  stratum  of  sand  or  pervious  sandstone  between 
two  strata  of  impervious  clay  or  rock,  the  percolation  from 
the    catchment-basin    or  valley  B  will   travel  toward  A   and 


Fig.  6. — Underground  Flow  in  Stratified  Rock. 

emerge  there.  The  hydraulic  gradient  will  be  the  line  BCy 
which  will  be  straight  if  the  material  and  thickness  of  the 
stratum  AB  be  constant.  A  well  at  D  would  then  overflow 
at  any  point  below  BC\  while  in  that  at  E  the  water  would 
rise  to  this  line  only  and  would  need  to  be  pumped.  If 
water  were  drawn  from  D,  the  hydraulic  gradient  would  be 
lowered  at  that  point.  If  lowered  to  the  point  F,  it  is 
probable  that  some  salt  water  would  reach  the  well;  as 
happened  at  Galveston,  Texas.  The  rise  and  fall  of  the  tide, 
causing  a  corresponding  change  in  the  hydraulic  gradient, 
will  cause  a  fluctuation  in  the  height  to  which  water  will  rise 
in  a  well  situated  similarly  to  E. 

The  amount  of  water  emerging  at  A  is  in  some  places  so 
great  as  to  occasion  fresh-water  springs  in  the  ocean;  as  off 
the  coast  of  South  Carolina,  and  the  Gulf  coast  of  Florida, 
where  such  springs  boil  up  through  a  depth  of  lOO  to  300  feet 
of  water  in  such  volume  as  to  make  it  dif^cult  to  row  a  boat 
above  them. 

Fig.  7  shows  a  section  through  the  St.  Peter  and  Potsdam 
sandstones  along  a  section  passing  through  Streator,  111.,  and 
Madison,  Wis.  These  two  strata  furnish  water  to  a  large 
number  of  cities  in  the  north-central  part  of  the  United 
States,    as   well   as  to  numberless   private   wells;    the   water 


138 


WATER-SUPPLY  ENGINEERING. 


rising    to    the    surface    in    a    large   number   of   wells    in    the 
Potsdam,  and  a  few  in  the  St.  Peter  sandstone.* 


ILLINOIS 


^^._  '^1-*       th^ OCEAN  LEVEL 


.ri<     /VV'* SECTION  OF  STRATA  IN  NORTHERN  ILLINOIS 
AND  SOUTHERN  WISCONSIN 

VERTICAL  SCALE  OF  FEET 
—    ^     >—     ' 

100  &00  1000 

HORIZONTAL  SCALE  OF  MILES 


0       10       20       30 


Fig.  7. — Underground  Flow  in  Stratified  Rock. 

In  Fig.  8  is  shown  the  condition  in  most  river  valleys, 
where  the  ground-water  from  the  hillside  flows  towards  and 


CLAY 

Ul'                              II                            a)00                           aUL'O                           ItAlij  jOOO      5100 

Fig.    8. — Cross-section    of    Valley    of    the    Fountain  qui    Bouille, 

Pueblo,  Col. 

into  the  river,  ordinarily  as  a  general  seepage.  The  flow  is 

in  most  cases  approximately  at  right  angles  to  the  trend  of 

the  valley.      But  if  the  soil  along  the  river  be  very  porous 


GROUXD-  WA  TER. 


139 


die  ground-water  may  flow  parallel  with  the  river,  being  in 
fact  but  a  part  of  its  flow;  as  the  Platte  River  in  Colorado 
and  Nebraska;  and  in  such  cases  the  ground-water  is  more 
constant  in  its  volume  than  the  visible  flow,  and  in  many- 
Western  rivers  is  being  more  relied  upon  as  a  source  of  supply. 
The  dam  across  the  Pacoima  Creek,  already  referred  to,  is  an 
instance  of  the  utilization  of  such  flow. 

The  well  in   Fig.  9  would  receive  largely  local  drainage, 
although   a   considerable    territory   in   some    instances  might 


ROCK  B 

Fig.  9. — Shallow  Wells. 

drain  to  and  by  such  shallow  wells.  That  at  A  would 
probably  run  practically  dry  in  times  of  drought,  while  in  B 
the  water,  when  there  was  any  underground  flow,  would  stand 
at  (T,  filling  up  to  this  point  each  time  after  the  well  was 
drawn  upon  and  lowered;  unless  the  draught  exceeded  the 
underground  flow  reaching  this  point,  when  the  level  at  C 
would  continually  fall,  but  the  depression  at  B  would  act  as 
a  reservoir,  supplying  water  after  A  was  entirely  dry. 

In  New  Jersey,  south  of  the  Raritan  River,  the  strata  for 
several  hundred  feet  down  are  alternately  blue  and  yellow 


Fig.  10. — Typical  Section  in  Central  New  Jersey. 
clays  and  marls,  and  sand  of  varying  thickness.      Most  of  the 
sand  strata  are  water-bearing.     The  flow  from  a  depth  of  425 


140  WATER-SUPPLY  ENGINEERING. 

feet  in  one  well  half  a  mile  from  shore  rose  to  6|  feet  above 
mean  high  tide,  indicating  an  outlet  into  the  ocean  at  least 
8  or  lo  miles  distant  (as  at  A,  Fig.  lo).  Similar  conditions  are 
found  along  the  Gulf  of  Mexico  and  over  a  considerable  part 
of  the  South  Atlantic  coast.      (See  Fig.  ii,  page  142.) 

'  Art.  39.     Classification  of  Ground-waters. 

Ground-waters  may  be  generally  classified  as  being  derived 
from — 

I.    Underlying  stratified  rock  deposits. 
II.    Drift. 
III.    Alluvial  and  marine  deposits. 
No.  I  may  be  subdivided  into — 

1.  Water  flowing  through  the  pores  of  rock  (Figs.  6 

and  7). 

2.  Streams  in  caves  and  subterranean  passages. 
Nos.  II  and  III  may  be  further  classified  as — 

3.  Water  derived   from  direct  percolation,  with  little 

lateral     transmission     or     hydrostatic     pressure 

(Fig-  9)- 

4.  Water  in  valley  bottoms  with  considerable  lateral 

transmission  and  small  hydrostatic  head  (Fig.  8). 

5.  Water  flowing  in  porous  strata  of  alluvial  or  marine 

deposit  or  glacial  drift  beneath  impervious  strata 

(Figs.  10  and  1 1). 
The  water  in  class  No.  i  is  received  from  rainfall  and  flow 
of  streams  at  and  over  the  outcrop  of  the  rock,  and  generally 
flows  for  long  distances  before  finding  an  outlet.  The  whole 
rock,  being  saturated  with  water  and  giving  it  up  slowly,  acts 
as  a  reservoir,  and  supplies  from  this  are  but  little  affected  by 
droughts  lasting  for  a  few  months  or  even  for  a  year  or  two. 
The  outcrop  often  covers  large  catchment  areas, — as  the 
St.  Peter  sandstone,  from  which  a  large  number  of  wells  in 


GRO  UND -  IV A  TER.  1 4 1 

Illinois,  Iowa,  and  Wisconsin  draw  their  supply;  and  under- 
lying this  the  Potsdam  sandstone,  which  has  an  outcrop  of 
about  14,000  square  miles  in  the  upper  Mississippi  valley, 
and  which  furnishes  a  largo  supply  in  the  States  just  named 
and  in  Minnesota  and  Michigan,  In  Ohio  and  Indiana  the 
Niagara  and  Trenton  limestones  furnish  abundant  supplies; 
and  in  the  Dakotas  and  northern  Nebraska  the  Dakota  sand- 
stone. 

Class  No.  2  derives  its  waters  largely  from  surface  streams 
and  direct  percolation,  which  find  sink-holes  or  open  seams 
in  the  rock,  and  dissolve  out  passages  for  themselves.  This 
generally  occurs  in  limestone,  and  as  the  water  is  not  under 
pressure  and  is  in  narrow  and  scattered  streams,  it  is  seldom 
used  for  supply  except  where  it  emerges  as  springs  or  rivers. 

Wells  of  the  third  class  are  generally  found  in  pockets  of 
drift  and  have  only  local  sources  of  supply.  They  are  shallow 
and  feel  quickly  the  effect  of  dry  or  wet  seasons.  They  are 
not  generally  suitable  for  public  supplies;  and  if  used,  the 
contributing  surface  must  be  carefully  guarded  from  pollution. 

Wells  of  the  fourth  class  furnish  the  supply  to  a  large  num- 
ber of  cities  in  this  country.  The  line  between  this  and  class 
No.  3  cannot  be  sharply  drawn,  but  this  class  has  a  much 
more  extensive  drainage  area.  The  alluvial  deposits  in  the 
southern  and  central  valleys  and  the  drift  in  the  northern 
third  of  the  United  States  afford  many  abundant  supplies  of 
this  class;  most  of  which,  however,  are  being  or  should  be 
abandoned  on  account  of  the  danger  of  pollution.  Shallow 
wells  and  galleries  are  constructed  for  utilizing  this  source  of 
supply;  and  the  interception  of  subsurface  river-flow,  as  at 
Pacoima,  also  belongs  to  this  class. 

The  waters  of  the  fifth  class  are  probably  used  more  exten- 
sively than  those  of  any  other.  The  Atlantic  coast  States 
from  New  Jersey  to  Georgia,  and  the  entire  Gulf  coast,  offer 
this  source  of  supply  in  the  alluvial  and  marine  deposits  at 


142  WATER-SUPPLY  ENGINEERING. 

depths  of  50  to  1000  feet.  Pensacola,  Fla. ,  obtains  from  this 
source  2,000,000  gals,  daily;  Memphis,  Tenn.,  10,000,000 
gals.;  Brooklyn,  N.  Y.,  25,000,000  gals.;  Fort  Wayne, 
Ind.,  6,000,000  gals.  In  western  Florida,  Mississippi,  and 
Louisiana  water  is  found  in  abundance  in  sand  and  fine 
gravel  interspersed  with  strata  of  vari-colored  clays.  West 
of  this  around  the  Mississippi  River  silt  predominates  and 
the  wells  yield  scantily.  In  eastern  Florida  the  wells  pene- 
trate cavernous  limestone,  spurs  of  the  Georgia  mountains, 
and  come  under  the  first  and  second  classes.  North  of  this 
are  again  water-bearing  sand  strata.  A  typical  Gulf  section 
is  shown  in  Fig.  11,  running  north  and  south  through  Pensa- 
cola.     Here   the   hydraulic   gradient  falls  about    i    in    4500 


,  \\fi  miles 

nsacola 
GULF    OF    MEXICO 


I                                                                                ,  IM  miles 
\t 12-miles >f. ►)  p^.^^ 


LOt^_^— -,r-t--r-:~--r^.. ,  ,.,...,■..--.... 


^AND;-;,."..'tl 


Fig.  II. — Section  of  Water-bearing  Stratum  ;  Pensacola,  Fla 

{s  =  .0002  +),  the  water  rising  16  or  17  feet  above  sea-level. 
At  Natchez,  Miss.,  the  water-bearing  sand  stratum  is  but  40 
feet  thick. 

The  impervious  strata  are  generally  clays  and  marls,  with 
occasionally  hard-pan,  and  vary  in  thickness  from  5  to  50  feet 
or  more.  The  pervious  material,  generally  sand,  sometimes 
runs  in  streaks  in  irregular  courses,  and  again  spreads  out  into 
thick  strata  miles  in  width  (Fig.  10).  There  can  therefore 
be  no  certainty  of  finding  a  particular  stratum  by  boring  at 
any  given  point,  but  this  is  largely  a  matter  of  chance.  The 
thicker  and  more  important  water-bearing  strata  generally 
extend  over  large  areas,  however,  and  may  be  found  with 
considerable  certainty  at  any  point  within  a  district  whose 
outer  limits  it  is  known  to  underlie. 


ground-  vva  ter.  1 43 

Art.  40.     Flow  of  Ground-water. 
The  general  direction  of  flow  of  waters  of  the  fourth  and 
fifth  classes  is,  in  the  majority  of  cases,  towards  the  sea,  along 
the  line  of  glacial  motion  if  in  drift,  or  diagonally  across  and 
down  a  valley  if  in  alluvial  deposits. 

When  a  well  is  pumped,  it  draws  water  from  the  sides  and 
below  as  well  as  above,  and  to  an  extent  depending  upon  the 
amount  the  water-surface  is  lowered  below  the  hydraulic 
gradient.  Waters  of  the  first  class  follow  in  their  flow  a 
course  from  their  outcrop  to  the  ocean  or  other  point  of  dis- 
charge, which  is  ordinarily  the  general  direction  of  pitch  of 
their  pervious  strata,  but  which  may  or  may  not  be  that  of 
the  ground-surface.  Those  of  the  second  class  follow  the 
faults  or  seams  and  the  general  pitch  of  the  strata,  occasion- 
ally sinking  from  one  stratum  to  the  next  lower. 

The  velocity  of  flow  depends  upon  the  slope  of  the  water- 
surface;  the  size  and  uniformity  of  the  grains  of  sand  or 
gravel,  or  of  the  pores  of  the  rock  through  which  it  flows; 
and  upon  the  temperature,  although  this  ordinarily  varies  but 
little.  In  finer  gravel  and  sand  the  velocity  is  found  to  be 
directly  proportional  to  the  slope,  while  in  coarse  gravel  it  is 
more  nearly  proportional  to  the  square  root  of  this.  The 
velocity  in  sand  may  be  represented  by  the  formula 

V=cd's* 
in  which  F=  velocity  in  feet  per  second; 

^  =  a  coefificient,  about  0.29  as  determined  by  a  few 

experiments; 
^=  the  effective  size  of  the  sand-grains  in  milli- 
meters. (Effective  size  of  sand  "  is  such 
that  \oic  of  the  material  is  of  smaller  grains 
and  90^  is  of  larger  grains  than  the  size 
given.") 

h 
s  =  -.  =:  sine  of  the  slope  of  the  hydraulic  gradient. 

*  Allen  Hazen,  in  Report  of  Mass.  Bd.  of  Health. 


144  WATER-SUPPLY  ENGINEERING. 

This  formula  is  not  considered  applicable  when  d  ex- 
ceeds 3. 

The  relative  area  of  open  spaces  in  sandy  soil  through 
which  the  water  flows  determines  the  quantity  of  flow.  In 
a  given  cross-section  this  area  will  generally  range  between 
.35  and  .60  of  the  total  area.  The  quantity  of  flow,  Q,  per 
unit  area  of  vertical  section  would  then  be  .35^10  .60V, 
On  Long  Island,  where  the  Brooklyn  water-supply  is 
obtained,  s  is  about  .0002  in  dry  weather  to  .002  in  wet. 
This  would  give  a  velocity  of  flow  in  dry  seasons,  assuming 
d=  0.5,  of  F  =  0.29  X  .25  X  .0002  =  .0000145  feet  per 
second,  or  1.25  feet  per  day;  and  (2=  -40  X  1.25  =  0.5 
cubic  feet  per  day  per  square  foot  of  vertical  section.  In  wet 
seasons  these  values  might  be  ten  times  as  great ;  s  being^ 
much  greater. 

Slopes  in  sand  of  30  to  50  feet  per  mile  are  found 
(^  =  .0057  to  .0091),  the  slope  generally  increasing  with  the 
fineness  of  the  material.  In  valleys  having  gravelly  soils  the 
cross-slope  is  generally  very  flat,  while  the  longitudinal  slope 
is  practically  that  of  the  river. 

Through  rock  the  velocity  of  flow  is  less  than  through 
sand,  owing  to  the  presence  of  the  interstitial  cementing- 
material,  but  practically  nothing  definite  is  known  upon  this 
subject.  In  the  Dakota  sandstone  the  distance  from  the 
outlet  in  the  Missouri  River  to  the  catchment  outcrop  in  the 
Rocky  Mountains  is  about  500  miles,  and  the  difference  in 
elevation  about  5000  feet,  giving  an  average  value  of  s  of 
.002 ;  but  it  is  thought  that  the  hydraulic  gradient  is  steeper 
than  this  near  the  outcrop,  since  it  is  flatter  in  Nebraska; 
probably  because  of  great  irregularities  and  faults  in  the 
strata  in  and  near  the  mountains. 

If  the  quantity  of  flow  through  a  given  material  due  to 
different  water-slopes  is  known,  we  can  approximate  the 
amount   of  water  available   from   such   material   in   a  given 


GRO  UND -  WA  TER.  1 4 5 

locality  by  sinking  two  wells  in  the  line  of  flow,  but  some  dis- 
tance apart,  and  noting  the  water-level  in  each;  or,  if  the 
direction  of  flow  is  not  known,  both  this  and  s  can  be  deter- 
mined by  sinking  three  wells  at  approximately  the  corners  of 
an  equilateral  triangle.  The  velocity  of  flow  can  be  found 
approximately  by  noting  the  time  elapsing  after  placing  salt 
in  one  well  before  it  makes  its  presence  known  in  another 
directly  below  it  in  the  line  of  flow.  If  the  upper  well  is 
artesian,  or  flowing,  rock  salt  may  be  inserted  in  a  bag  and 
lowered  into  this  well,  the  flow  from  it  being  then  immedi- 
ately stopped. 

If  a  well  be  pumped,  the  water-surface  is  lowered  below 
the  original  hydraulic  gradient,   reas^ssss 
the  plane  of  the  gradient  being 


drawn     down     in     the    manner  °' 


shown  in    Fig.    12;    the  extent 
and  depth  of  the  depression  in- 
creasing   with    the     amount    of  Fig,  12. — Effect  of  Pumping  on 
water  pumped.  Ground-water. 

Since  the  velocity  of  flow  must  increase  as  the  well  is 
approached,  the  slope  of  the  water-surface  increases  corre- 
spondingly, and  a  curved  surface  is  formed,  the  shape  of  which 
depends  upon  the  form  of  the  equation  for  V.  In  Brooklyn, 
in  1886,  the  water-level  4300  feet  from  a  well  which  was 
being  pumped  fell  6  inches,  at  2300  feet  the  fall  was  26 
inches,  and  at  300  feet  it  was  56  inches.  In  another  Brooklyn 
well  the  base  of  the  depression  was  about  4000  feet  in 
diameter  when  the  water  was  lowered  8  feet  at  the  well.  In 
another  the  diameter  was  5000  feet  when  the  water  was 
lowered  i  5  feet  * 

Sou-ie  time  must  elapse  afl;er  pumping  begins  before  the 
cepression    assumes    a    final  shape,   since  the  water  formerly 

*  In  Memphis  the  curve  was  fairly  well  represented  by  x  =  — ■—    "' 


y"-*  +  50- 
See  Engitteeriftg  News  for  Oct.  2,  1902. 


146  WATER-SUPPLY   EXGINEERJNG. 

filling  it  must  first  be  exhausted.  Similarh',  the  depression 
will  fill  gradually  when  pumping  ceases.  Thus,  a  set  of  wells 
in  Brooklyn  was  pumped  for  twenty  days,  at  a  rate  of 
5,000,000  gals,  per  day,  the  ground-water  being  lowered 
14  feet;  and  the  depression  was  not  filled  until  the  twelfth 
day  after  pumping  ceased.  If  the  diameter  of  the  depression 
was  5000  feet,  and  the  soil  was  33$^  voids,  and  60,'^  of  the 
contained  water  was  yielded,  the  amount  of  water  to  be 
replaced  was  probably  about  95,000,000  gals. — approxi- 
mately the  total  amount  pumped.  If  this  was  the  case,  the 
depression  might  not  yet  have  assumed  its  permanent  form. 

If  wells  be  located  too  near  each  other,  their  cones  of 
depression  will  intersect,  and  the  flow  of  each  or  some  will  be 
reduced.  They  should  be  placed  across  the  direction  of 
flow,  otherwise  the  upper  wells  will  leave  little  water  for  the 
lower  ones,  which  thus  become  almost  useless. 

Art.  41.  Wells. 
The  method  ordinarily  adopted  for  intercepting  ground- 
water of  the  first  and  fifth  classes,  and  frequently  of  the  third 
and  fourth  classes,  is  that  of  sinking  wells  into  and  through 
the  water-bearing  strata.  For  waters  of  the  third  and  fourth 
classes  large  dug  wells  are  frequently  employed,  walled  in 
with  brick  or  stone  (see  Fig.  66,  page  398);  but  for  deep 
wells,  and  in  many  cases  for  shallow  ones,  small  pipe-wells  2:^^ 
to  12  inches  diameter  are  sunk  (see  Plate  XVII,  peige  397). 
These  latter  are  frequently  carried  to  great  depths  and  through 
all  kinds  of  material.  At  St.  Augustine,  Fla.,  is  a  12-inch 
well  1400  feet  deep  through  shale  and  limestone;  at  Charles- 
ton, S.  C,  is  a  5^-inch  well  1900  feet  deep;  at  Atlanta,  Ga., 
is  one  2044  feet  deep ;  at  Paris,  France,  is  one  2359  ^^<^t  deep ; 
at  St.  Louis  is  one  3850  feet  deep;  in  West  Virginia  is  one 
4500  feet  deep  (dry);  and  at  Pesth  is  one  8140  feet  deep. 
Table  No.  42  gives  a  list  of  some  of  the  larger  cities  and 
towns  of  the  United  States  using  ground-water  as  a  supply. 


GRO  UND-  WA  TER. 
Table  No.  42. 


147 


SOME   OF    THE    LARGER    CITIES    AND    TOWNS  OF    THE    UNITED    STATES 
HAVING    SUBTERRANEAN    SOURCES    OF    WATER-SUPPLY. 

(D.  W.  Mead  in  Trans.  Am.  Soc,  C.E.,  vol.  xxx.) 


Popula- 

City. 

1         State. 

tion, 
1890. 

Source. 

Geological  source. 

Anniston 

Alabama 

9.998 

Springs 

Appleton 
Akron 

Wisconsin 

11,869 

3  artesian  wells 

St.  Peter  sandstone 

Ohio 

27,601 

Artesian  wells 

Atlantic  City- 

New  Jersey 

'3.055 

Large  well 

Aurora 

Illinois 

19,688 

2  artesian  wells 

St.  Peter  and  Potsdam 
sandstone 

Beloit 

Wisconsin 

6.31S 

Large  well 

Trenton  rock 

Big  Rapids 

Michigan 
Xew  York 

5 .303 

Drive  wells 

Drift 

Brooklyn 

806,343 

"         " 

" 

Brunswick 

Georgia 

8,459 

Artesian  wells 

Cedar  Rapids 

Iowa 

18,020 

"          " 

Potsdam  sandstone 

Charlestown 

S.  Carolina 

60,000 

3  artesian  wells 

Clinton 

Iowa 

13.619 

4 

Potsdam  and  St.  Peter 
sandstone 

Columbus 

Ohio 

88,150 

Filter-gallery 

Drift 

Dayton 

" 

61,220 

65  8-in.  tube-wells 

" 

Des  Moines 

Iowa 

5o.°93 

Large  well 

Dixon 

Illinois 

S,i6i 

2  artesian  wells 

Potsdam  sandstone 

Dubuque 

Iowa 

30,311 

Artesian  wells 

"                " 

Fond  du  Lac 

Wisconsin 

12,024 

5  artesian  wells 

St. Peter  sandstone  and  drift 

Freeport 

Illinois 

10,189 

18  drive  wells 

Drift 

Fresno 

California 

io.8i8 

10  artesian  wells 

200  to  600  feet  deep 

Galena 

Illinois 

5.635 

Artesian  wells 

Potsdam  sandstone 

Galesburg 

" 

15,264 

Drive  wells 

Drift 

Grand  Islani^ 

Nebraska 

7.536 

"        " 

Platte  River  Valley 

Jamestown 

New  York 

16,038 

Artesian  wells 

Jackson 
Joliet 

Michigan 

20,793 

Illinois 

33,264 

Drive     and      artesian 

Drift  and  St.Peter  sandstone 

wells 

Jacksonville 

Florida 

17,201 

4  artesian  wells 

Cretaceous  strata 

Kearney 

Nebraska 

8,074 

Drive  wells 

Platte  River  Valley 

Kalamazoo 

Michigan 

17.853 

2  large  wells 

Drift 

Lincoln 

Nebraska 

58,000 

2     "            " 

" 

Macon 

Georgia 

32,746 

Springs 

Memphis 

Tennessee 

64,495 

Artesian  wells 

Cretaceous  strata 

Mansfield 

Ohio 

13.473. 

16  wells,  2  springs 

Drift 

Montgomery 

Alabama 

21,883 

Artesian  wells 

Michigan  City 

Indiana 

10,776 

Springs 

Drift 

Muncie 

" 

11.345 

Artesian  wells 

Manistee 

Michigan 

12,812 

50  drive  wells,  i  large 

well 
76  drive  wells 
Underflow 

Drift 

New  Brighton 

New  York 

16,423 

.. 

Nashville 

Tennessee 

76,168 

Cumberland    River,     filter- 

gallery 

Oshkosh 

Wisconsin 

«,836 

Artesian  well 

Lake  Winnebago  for  fire 
protection 

Peoria 

Illinois 

41,024 

Large  well 

Gravel  in  ancient  bed  of 
Illinois  River 

Pine  Bluff 

Arkansas 

9.9Si 

Drive  wells 

Pensacola 

Florida 

11,750 

16  drive  wells 

Pittsburg 

Kansas 

6,697 

Artesian  wells 

Rockford 

Illinois 

23,584 

9  artesian  wells 

Potsdam  and  St.  Peter  sand- 
stone 

Savannah 

Georgia 

43,'86 

Artesian  wells 

Stockton 

California 

•4.424 

Artesian  well 

Selma 

Alabama 

7,622 

3  artesian  wells 

South  Bend 

Indiana 

21,819 

32       "            " 

Drift 

Springfield 

Illinois 

24.963 

Well  and  filter-gallery 

" 

Sioux  City 

Iowa 

45,000 

Drive  wells 

Winona 

Minnesota 

18,208 

2  large  wells 

Mississippi  underflow 

148  WATER-SUPPLY  ENGINEERING. 

Wells  are  used  for  irrigation  to  a  small  extent  in  the  West. 
In  the  fourteen  Western  States  and  Territories,  in  June  1890, 
3930  deep  wells  furnished  irrigation  for  51,896  acres,  or  1.43^ 
of  the  total  area  irrigated.  The  total  number  of  deep  wells 
in  those  States  at  that  time  was  8097,  their  average  depth 
210  feet,  and  average  discharge  54.43  gals,  per  minute;  giving 
a  duty  of  109  acres  per  second-foot. 

In  order  that  all  surface-water  may  be  excluded,  the  well- 
casing  should  always  be  tight  from  the  surface  down  to  a 
thick,  impervious  stratum  of  clay  or  rock,  with  which  it 
should  make  a  tight  joint;  or,  if  there  are  no  such  strata, 
the  entire  casing  should  be  tight  except  at  and  near  the 
bottom,  to  exclude  local  percolation  which  has  not  been 
filtered  through  considerable  depth  of  soil.  For  the  same 
reason  the  top  should  be  tightly  closed,  or  should  be  carried 
above  the  reach  of  surface-water. 

Wells  sunk  to  ground- water  whose  hydraulic  gradient  lies 
above  the  surface  at  that  point,  and  which  consequently 
overflow,  are  generally  called  artesian  wells.  But  by  many  this 
term  is  used  for  either  class  of  wells;  the  difference  after  all 
lying  solely  in  the  elevation  of  the  ground-surface  at  that  point. 

It  is  almost  always  necessary  or  desirable  to  pump  from 
a  deep  well,  whether  artesian  or  not;  since  it  is  generally 
cheaper  to  increase  the  supply  from  a  few  wells  by  pumping 
than  to  sink  more  wells.  There  may  be  exceptions  in  the 
cases  of  small  supplies  which  one  or  two  artesian  wells  can 
furnish  by  gravity. 

The  amount  of  water  obtainable  from  underground  has 
already  been  referred  to.  This  cannot  all  be  intercepted  by 
wells  in  any  practicable  way,  10  or  25  per  cent  probably 
being  the  maximum  amount  obtainable  under  any  conditions. 
The  amount  obtainable  by  a  given  well  can  never  be  predicted 
with  any  accuracy  except  by  comparison  with  other  wells  in 
the  same  stratum. 


GRO  UND-  WA  TER.  I49 

For  a  short  time  after  beginning  to  pump  a  well  the 
delivery  may  increase,  owing  to  the  opening  of  channels  in 
the  water-bearing  material.  But  if  the  pumping  increase 
the  temporary  yield  beyond  the  natural  local  ground-flow, 
and  especially  if  this  be  true  for  a  number  of  wells  in  one 
neighborhood,  the  ground-storage  may  be  drawn  upon,  the 
hydraulic  gradient  lowered,  and  the  natural  yield  diminished. 
Thus,  at  Rockford,  111.,  where  a  number  of  wells  are  sunk 
into  the  Potsdam  sandstone,  the  gradient  fell  10  feet  in  six 
years. 

A  lO-inch  well  in  Brooklyn  no  feet  deep  has  yielded 
150,000  gals,  per  day;  a  5 -inch  well  at  Rockford,  111.,  1800 
feet  deep,  259,000  gals.,  and  a  6-inch  one  at  the  same  place 
364,000  gals,  per  day.  The  Ponce  de  Leon  12-inch  well  at 
St.  Augustine  yields  10,000,000  gals,  per  day;  and  at 
Charleston,  S.  C,  a  5^-inch  well  1900  feet  deep  yields 
1,250,000  gals,  daily.  The  amount  of  yield  depends  to  a 
certain  extent  upon  the  freedom  with  which  water  can  enter 
the  well,  and  has  often  been  diminished  or  altogether  stopped 
by  a  choking  of  the  inlet  openings.  Increasing  the  size  of 
the  well-casing  increases  the  flow  chiefly  by  decreasing  the 
velocity  and  friction  within  itself.  If  a  deep-well  pump  is  to 
be  used,  the  size  of  the  casing  must  be  adapted  to  this.  (See 
page  397.) 

Art.  42.  Infiltration-galleries. 
When  the  ground-flow  near  the  surface,  as  in  Fig.  6, 
page  137,  is  to  be  used  for  a  supply  a  number  of  wells, 
driven  or  dug,  may  be  employed;  but  a  larger  quantity  can 
ordinarily  be  obtained  by  use  of  a  long  crib  placed  at  right 
angles  to  the  direction  of  flow  and  below  the  ground-water 
surface  (see  Fig.  6^ ,  page  399).  This  is  generally  placed 
near  a  river,  not  to  utilize  the  river-water,  which  in  most 
cases  is  impossible,  but  because  the  ground-flow  increases  in 


ISO 


WATER-SUPPLY  ENGINEERING. 


volume  as  its  outlet  is  approached.  Infiltration-galleries  are 
made  of  wood,  brick,  or  stone  in  the  shape  of  a  small,  long 
gallery,  with  openings  in  the  sides  and  bottom  through  which 
the  water  enters.  A  well-located  gallery  will  intercept  almost 
all  of  the  ground-flow  in  its  locality,  which  is  pumped  from 
it  direct  or  led  from  it  by  pipes  or  channel  to  a  pump-well. 

An  infiltration-gallery  may  be  considered  as  a  large, 
oblong  well,  and  the  statements  above  relative  to  ground-flow 
apply  to  these  as  well  as  to  wells. 

At  Newton,  Mass.,  and  some  other  cities  wells  are  sunk 
along  the  line  of  the  filter-gallery  and  discharge  into  this, 
thus  uniting  the  supplies. 

An  infiltration-gallery  is  sometimes  placed  across  the 
channel  of  a  river  which  has  a  large  underground  flow,  to 
intercept  this.  This  method  is  particularly  applicable  to 
some  of  our  Western  rivers,  where  the  underground  flow  is  at 
most  times  greater  than  the  visible.  The  underflow  of  the 
Platte  River  was  thus  used  for  the  Denver  water-works.  In 
many  or  most  of  such  cribs  considerable  water  is  drawn  from 
the  visible  supply,  when  there  is  any. 

The  great  probability  that  water  so  near  the  surface  will 
be  polluted  has  led  to  the  abandoning  of  many  infiltration- 
galleries  in  the  Eastern  States;  and  they  are  recommended 
for  such  localities  only  as  are  beyond  any  sources  of  pollution. 
The  probability  of  such  water  being  polluted  in  and  near 
cities  is  shown  by  the  following  analysis  of  water  from  the 
subdrains  of  the  Framingham  sewers  before  the  latter  were 
put  into  use,  the  pollution  probably  being  from  cesspools. 


Ammonia. 

Nitrates. 

Nitrites. 

Total 
Nitrogen. 

Free. 

In 
Solution. 

In  Sus- 
pension. 

Chlorine. 

.0648 

.0058 

.0000 

.6000 

.0036 

.6665 

3.62 

GRO  UND-  WA  TER, 


151 


Art.  43.     Springs. 

When  the  stratum  through  which  any  underground  water 
flows  comes  to  the  surface  at  a  point  lower  than  the  catch- 


TiG.   13. — Spring  at  Outcrop. 

ment  area,  the  water  emerges  as  a  spring,  as  at  D,  Fig.  13, 
or  as  seepage.  Also  where  faults  occur  the  water  may  rise 
vertically  to  the  surface,  as  at  yi.  Fig.  14  (but  is  more  likely 


Fig.  14. — Spring  from  a  Fault. 

to  fall  to  a  lower  pervious  stratum).      Such  a  spring  at  San 

Antonio,  Tex.,  yields  50,000,000  gals,  daily.      Underground 

water    may  also  rise  through   a 

stratum  of   clay  or  hardpan,   as 

at  D,  Fig.  15.  ^t^i 

It    is    evident    that    spring- 
water  is  the  same  in  origin  and 
character  as  water  obtained  by     ^''''  ^5--SpRing  in  Hardpan. 
wells  from  the  same  stratum;  those  shown  in  figures  14  and 
15  being  practically  natural  wells. 

Springs  may  be  simply  walled  in  without  further  develop- 
ment ;  but  in  many  cases  the  supply  may  be  increased.     A 


152  WATER-SUPPLY   ENGINEERING. 

spring  is  often  but  one  of  a  number  of  points  of  emergence  of 
a  given  stratum  of  ground-flow,  although  the  others  may  be 
only  a  general  seepage,  and  may  be  some  distance  away.  A 
trench  or  infiltration-gallery  placed  at  right  angles  to  the 
direction  of  flow  will  then  intercept  much  more  than  the 
yield  of  the  spring;  or  a  lowering  of  the  outlet  may  draw 
from  other  channels  draining  the  same  catchment  area.  If 
there  are  one  or  more  porous  strata  near  and  parallel  to  the 
surface  of  a  hillside,  horizontal  tunnels  may  be  driven  into 
the  hill  to  intercept  water  from  these;  as  is  done  at  Oakland, 
Cal. 

The  deepening  and  enlargement  of  a  spring  and  drawing 
down  of  the  water-level  will  often  cause  a  considerable 
increase  in  the  flow  at  the  expense  of  other  springs  in  the 
neighborhood.  A  spring  yielding  75,000  gals,  per  day  was 
so  developed  in  this  manner  by  the  author  as  to  yield  more 
than  double  this  amount  and  furnish  the  supply  for  a  small 
community. 

Art.  44.     Amount  of  Ground-water  Available. 

The  amount  of  water  flowing  in  a  given  stratum  may,  as 
already  stated,  be  estimated  by  the  formula  (9  =  aF,  a  being 
the  area  of  open  spaces  in  a  vertical  section  of  the  stratum 
across  the  line  of  flow,  and  F  being  obtained  by  test-wells, 
or  by  the  formula  given  on  page  143.  But  the  total  flow  in 
a  given  stratum  cannot  continuously  exceed  the  amount 
entering  it  by  percolation  from  the  catchment  area;  although 
it  may,  temporarily,  by  drawing  upon  the  ground-storage. 

The  percolation  may  vary  within  very  wide  limits,  but 
will  probably  be  about  60  to  70  per  cent  of  the  annual  rainfall 
in  sand,  25^  in  sandstone,  15^  in  limestone,  and  much  less  in 
clay,  granites,  etc.  English  experimenters  have  found  about 
35^    to    percolate    through    gravelly  loam  and    chalk.     The 


GRO  UND-  WA  TER.  1 5  3 

ground-flow  may  receive  water  from  not  only  its  own  outcrop, 
but  also  from  that  of  any  porous  strata  above  it.  In  such  a 
case  all  such  contiguous  porous  strata  may  be  considered 
together  in  figuring  the  catchment  area.  A  well  into  the 
lowest  of  these  will  draw  from  the  others  as  well  as  from  its 
own  flow. 

The  total  percolation  into  a  stratum  must  generally  fill 
and  flow  through  all  parts  of  such  stratum  which  are  below 
the  hydraulic  gradient.  It  is  therefore  possible  that  the 
volume  per  square  foot  of  section  flowing  at  any  point  may 
be  either  less  or  greater  than  the  average  percolation  per 
square  foot  of  vertical  section  at  the  outcrop;  and  this  latter 
section  may  be  but  a  small  percentage  of  the  actual  exposed 
area,  as  at  BC,  Fig.  13. 

Waters  of  the  third  and  fourth  classes  are  generally  derived 
from  the  rainfall  over  the  entire  area  of  the  basin  or  valley  in 
which  they  are  found,  augmented  by  a  considerable  ground- 
and  surface-flow  from  the  adjacent  hillsides.  In  dry  weather 
the  flow  is  in  some  instances  reversed,  and  water  enters  the 
ground  from  the  river  or  lake.  This  is  generally  true  when 
the  soil  is  of  gravel  or  coarse  clean  sand,  and  when  the  river 
carries  little  silt.  In  any  soils  the  river  channel  will  probably 
be  impervious  if  the  river  at  times  carries  much  clay  or  loam 
in  suspension. 

The  exceeding  slowness  of  flow  through  rock  results  in 
this  flow  being  almost  constant  through  all  seasons  and  years; 
the  more  extensive  the  stratum  the  greater  being  the  uni- 
formity. In  sand  and  gravel  the  flow  is  more  subject  to 
variation  from  this  cause,  but  here  also  the  more  extensive 
the  stratum  the  less  the  variation.  When  the  stratum  feels 
the  effects  of  droughts  the  storage  capacity  of  the  soil  may 
be  called  upon.  If  in  Fig.  16,  for  instance,  the  ground-water 
stand  at  the  upper  dotted  line  during  the  average  season,  it 
might  during  a  dry  one  be  gradually  lowered  to  the  lower 


154 


WATER-SUPPLY  ENGINEERING, 


line,  the  pumps  having  withdrawn  not  only  the  contemporary 
seepage,  but  in  addition  an  amount  represented  by  the  fall 
in  water-level.  It  is  evident  that  the  ability  of  a  stratum  to 
tide  over  a  drought  is  measured  by  its  area,  depth,  proportion 
of  voids,  and  percentage  of  contained  water  which  can  be 
abstracted.  The  volume  of  voids  will  vary  probably  from  20 
to  45  per  cent  of  the  total  volume,  depending  little  on  the 
size   of    grain    but    much    on    the   uniformity   of  size.      The 


Fig.   16. — Ground-storage. 

amount  of  the  contained  water  which  the  soil  will  yield 
depends  upon  the  capillarity  and  hence  the  fineness  of  grain. 
Thus,  gravel  will  give  up  practically  all  and  clay  almost  none 
of  the  contained  water.  Ordinary  sand  will  surrender  60  to 
70  per  cent,  and  fairly  permeable  soils  50  to  60  per  cent,  of 
their  water.  An  average  sandy  loam  will  therefore  yield 
about  20^  of  its  total  volume.  A  stratum  of  10  square  miles 
area  would  thus  yield  about  418,000,000  gals,  per  vertical 
foot  of  saturated  soil,  i.e.,  soil  below  the  ordinary  ground- 
water level.  If  the  daily  supply  for  six  months  was  10,000,- 
000  gals.,  while  12,000,000  was  required,  the  additional 
might  be  obtained  by  lowering  the  ground-water  an  average 
of  ten  inches.  The  area,  however,  must  be  that  of  the 
ground-water  surface  and  not  of  the  ground ;  and  as  the  water 
surface  is  lowered  its  area  contracts,  and  hence  the  water- 
level  falls  more  quickly  the  longer  the  ground-storage  is  called 
upon.  This  ground-storage  may  be  an  important  considera- 
tion with  waters  of  the  third  and  fourth  classes. 

The  amount  of  ground-water  considered  in  this  article  is 


GKO  UXD-  WA  TER.  155 

the  total  flow;  but  it  must  be  remembered  that  in  almost  no 
case  is  all  of  this  available., 

Art.  45.     Quality  of  Ground-water. 

Ground-water  being  but  the  intercepted  ground-flow  of 
the  yield  of  a  drainage  area,  the  remarks  in  Art.  34  applying 
to  such  flow  are  applicable  to  ground-water.  But  the  latter 
is  unmixed  with  surface-water,  and  if  from  deep  wells 
ordinarily  furnishes  a  supply  free  from  organic  pollution  and 
colorless. 

The  analysis  on  page  150  shows  an  extreme  case  of  the 
pollution  of  the  upper  ground-waters;  but  there  is  always 
great  danger  of  such  pollution  when  the  seepage  water  is 
from  an  inhabited  areao 

With  deep  wells,  particularly  when  the  water-bearing 
stratum  is  overlaid  with  an  impervious  one,  there  is  little 
danger  of  such  pollution ;  although  disease-germs  have  been 
known  to  travel  for  a  considerable  distance  through  such 
strata  when  very  porous,  living  for  a  week  or  more  after 
entering  the  ground. 

Springs  are  subject  to  such  contamination  when  from 
shallow  surface  strata  or  from  deep  ones  which  are  very 
porous.  The  best-known  illustration  of  the  latter  is  the  case 
of  Lausen,  Switzerland,  where,  in  1872,  typhoid  germs  were 
found  to  pass  through  a  hill  and  transfer  an  epidemic  from 
one  side  of  this  to  the  other.  The  porous  stratum  here 
filtered  out  flour  placed  in  the  water,  but  was  comparatively 
coarse,  since  the  water  passed  through  the  hill  in  a  few  hours. 
A  spring  which  shows  little  effect  from  droughts  will  generally 
be  from  a  deep  and  extensive  stratum,  and  free  from  all 
organic  impurities. 

Deep  wells,  and  springs  from  deep  and  extensive  strata, 
usually  give  a  water  containing  little  free  oxygen  and  much 


156 


WAT ER-SUPPLY  ENGINEERING. 


mineral  matter,  the  oxygen  formerly  present  having  united 
with  the  latter.  The  Grenelle  well  at  Paris,  1780  feet  deep, 
contains  no  oxygen.  The  Ponce  de  Leon  well  contains  319 
parts  per  100,000  of  mineral  matter,  nine  minerals  being 
recognized,  195.8  parts  being  sodium  chloride.  "  Old  Faith- 
ful '*  geyser,  Yellowstone  Park,  contains  139  parts  of  mineral 
matter,  63.9  being  sodium  chloride.  These  waters  are  not 
potable.  The  following  analyses  of  Brooklyn  City  water 
from  deep  and  shallow  wells  show  an  average  amount  of 
mineral  matter  for  such  waters. 

Table  No.  43, 

ANALYSES    OF    BROOKLYN,     N.     Y.,     DRIVEN-WELL     WATER. 


Spring  Creek  ;  old  driven-well 
plant 

Jameco  Station  ;  driven  wells 
(shallow) 

Jameco  Station  ;  driven  wells 
(deep) 

Hempstead  stream 


O   %i 


Residue  on  Evaporation. 


C3     Q 


19.44 
17-45 

12.50 
5-58 


4.04 
4-45 


2.00 
1.77 


15.40 
13  00 


10.50 
3-8i 


.0005 
•04S3 

.07S4 
.2122 


.0015 

.0140 

•  0156 
.0209 


Spring  Creek  ;  old  driven-well 
plar>t 

Jameco  Station  ;  driven  wells 
(shallow) 

Jameco  Station  ;  driven  wells 
(deep) 

Hempstead  stream 


Chlorine  as 


o 


1.2857 
3.2500 

0.4500 
o . 8000 


t2  rtt/3U 


2.II86 
5-3560 

0.7420 

I. 3183 


Nitrogen  as. 


4510 
.0426 

.0716 

.1875 


None 


.0006 


Hardness, 
Equivalent  to 
Carbonate  of 
Lime. 


II. 0214 
5-0750 


9 . 2000 

1-7375 


8.0929 

5-0750 

8 . 7000 
1.7025 


GROUND-WATER.  '  1 57 

The  high  ammonia  and  chlorine  in  the  old  Jameco  Station 
-well  would  seem  to  imply  pollution  by  sewage;  although  the 
■chlorine  may  be  due  to  the  fact  that  the  ocean  is  but  a  short 
distance  away.  The  mineral  matter  in  the  wells  is  seen  to 
be  high  as  compared  with  the  Hempstead  Stream  surface- 
water^ 

Ground  water  is  generally  cooler  than  surface-waters  in 
summer,  and  warmer  in  winter;  that  of  wells  ranging  iii 
Massachusetts  between  49°  and  53°,  and  of  filter-galleries  and 
shallow  wells  between  48°  and  6"]° .  Some  ground-waters  arc 
very  warm,  however;  as  the  Ponce  de  Leon  well,  which  has  a 
temperature  of  86°;  and  the  **  boiling  springs  "  found  in  the 
Yellowstone  Park  and  several  other  parts  of  the  world. 

QUERIES. 

13.  Find  an  equation  which  will  approximatelj-  represent  the 
curve  of  ground-water  depression  at  the  Brooklyn  well,  data  for 
which  are  given  in  Art.  40,  page  145. 

14.  If  a  crib  100  feet  long  intercept  all  the  ground-flow  behind 
and  over  it  of  a  stratum  10  feet  thick,  the  slope  of  the  ground-water 
being  2c  feet  per  mile,  ^/=o.5,  <r  =  .29,  and  the  area  of  inter- 
stices in  a  cross-section  being  .4,  what  is  the  maximum  amount  of 
water  such  crib  could  intercept  ?  What  area  of  catchment-basin  at 
Denver  is  necessary  to  supply  this  amount,  assuming  40^  of  the 
rainfall  to  pass  oft  as  ground-flow  ^ 


CHAPTER    IX. 
GRAVITY   SYSTEMS. 

Art.  46.     Definitions. 

A  SUPPLY  of  water  of  the  requisite  quality  and  quantity 
having  been  decided  upon,  and  the  amount  of  storage  neces- 
sary, if  any,  having  been  calculated,  there  remains  the 
problem  of  conducting  this  to  the  consumer  and  distributing 
it  in  such  quantities  as  shall  be  necessary,  and  under  the 
necessary  head. 

The  methods  of  bringing  the  water  from  its  source  to  the 
point  of  utilization  may  be  generally  divided  into  two  classes 
—  Gravity  and  Pumping  Systems.  In  the  former  the  eleva- 
tion of  the  source  above  the  point  of  utilization  is  so  great 
that,  if  proper  conduits  be  provided,  the  water  will  flow  by 
gravity  from  the  former  to  the  latter;  supplying  also  the 
pressure-head  necessary  in  the  case  of  city  supplies.  In 
pumping  systems  the  source  has  not  sufficient  elevation  to 
provide  this  flow  and  pressure,  and  the  water  must  be  raised 
or  given  sufficient  pressure  by  some  form  of  pump.  The 
source  may  be  higher  than  any  point  of  utilization,  and 
pumping  still  be  necessary  to  overcome  friction  or  to  raise  the 
water  over  an  intervening  ridge  or  other  elevation. 

Art.  47.     Head-works  of  Gravity  Systems. 

A  gravity  system  can  be  divided  into  three  parts:  the 
distribution  system,  or  the  various  main  and  lateral  pipes  or 
channels  through  which  the  water  is  distributed ;  the  main 

158 


GRAVITY   SYSTEMS,  159 

conduit,  which  carries  the  water  from  the  source  to  the  dis- 
tribution system ;  and  the  head-works,  by  which  the  water  is 
intercepted  and  introduced  into  the  main  conduit.  As  a  part 
of  the  head-works  may  be  considered  all  which  is  necessary 
to  provide  the  water  at  the  proper  rate  and  head,  such  as 
impounding-  or  distributing-reservoirs,  and  of  the  proper 
quality,  such  as  filters  or  sedimentation-basins. 

The  essential  part  of  the  head-works  of  any  gravity  supply 
are:  a  dam  (in  a  very  few  cases  unnecessary),  and  an  inlet  to 
the  conduit,  with  valves  for  regulating  the  flow  into  the 
same.  In  the  great  majority  of  gravity  supplies  some  storage 
is  necessary,  for  which  an  impounding-  or  storage-reservoir 
must  be  supplied.  If  this  reservoir  is  at  a  considerable  dis- 
tance from  or  above  the  point  of  utilization,  a  distributing- 
reservoir  is  frequently  interposed  in  the  conduit  near  such 
point,  to  relieve  the  distribution  system  of  excessive  pressure, 
lessen  the  liability  of  interruption  of  service,  and  permit  the 
discharge  of  large  amounts  of  water  during  short  periods. 
The  effecting  of  the  first-named  result  by  a  lower  distributing- 
reservoir  is  apparent.  The  second  result  is  usually  obtained 
because,  should  there  be  a  break  in,  or  other  interruption  in 
the  service  of,  the  conduit  between  the  impounding-  and  dis- 
tributing-reservoirs, the  latter  would  continue  the  supply  for 
some  part  at  least  of  the  time  required  to  repair  the  conduit. 
A  short  conduit  under  pressure  from  a  service-reservoir  will 
deliver  water  at  an  unusually  high  rate  with  less  loss  of  head 
than  will  a  long  one,  since  the  total  loss  of  head  varies  with 
the  length;  and,  moreover,  a  size  of  conduit  adapted  to  a 
given  (temporary)  high  rate  of  discharge  may  be  carried  from 
the  distributing-reservoir  only,  which  can  be  fed  by  the  con- 
tinuous flow  through  a  much  smaller  one  from  the  intake, 
thus  saving  in  the  cost  of  the  latter  line.  If,  however,  the 
utilization  is  continuous  and  constant  in  volume,  the  last 
reason  for  the  use  of  a  distributing-reservoir  is  not  applicable. 


I60  WATER-SUPPLY  ENGINEERING. 

For  example,  in  fig.  17  a  city,  A,  is  to  be  supplied  with 
water  from  a  storage-reservoir,  C,  there  being  a  hill,  By 
but  one  fifth  the  distance  from  A  that  C  is,  which  hill  is 
200  feet  above  A  and  25  feet  below  C.  A  supply  for  fire 
purposes  or  other  heavy  draught  under  a  100-foot  pressure,, 
to  pass  which  would  require  a  20-inch  pipe  from  B  to  Ay 
would  require  a  27-inch  pipe  from  C  to  A\  while  an  average 
supply  of  one  fourth  this  amount,  which  would  keep  B  full 
c 


Fig.  17. — Distributing-reservoir. 

from  day  to  day,  would  require  between  B  and  C  but  a 
i6-inch  pipe. 

In  addition  to  the  above  reasons,  there  is  convenience 
and  safety  in  having  complete  control  of  the  supply  to  the 
conduit  at  a  point  near  the  city. 

When  it  is  not  necessary  to  store  water  in  order  to  obtain 
a  continuous  supply,  a  storage-reservoir  is  not  required;  but 
even  in  this  case  it  is  generally  necessary  to  place  a  dam 
across  the  stream  (which  is,  in  most  gravity  supplies,  a  small 
one)  to  furnish  sufficient  depth  and  decreased  velocity  for  the 
proper  intaking  of  the  water,  and  to  facilitate  excluding  sand 
and  gravel  from  the  conduit. 

Art.  48.     Storage-reservoirs:  Location. 

A  storage-reservoir  for  a  gravity  supply  is  generally  placed 
on  the  course  of  the  stream  or  streams  furnishing  this  supply; 
and  in  most  cases  is  formed  by  placing  a  dam  across  a  valley. 
If  the  valley  above  this  point  be  long  and  narrow,  the  reser- 
voir will  be  of  this  shape;  and  in  many  cases  two  or  more 


GRA  VIT Y   SYS TEMS.  1 6 1 

valleys  of  contributing  streams  are  united  in  one  reservoir; 
but  if  a  natural  basin  can  be  found  at  a  convenient  elevation 
and  location  this  is  to  be  preferred.  It  is  desirable  that  the 
enclosing  hills  be  steep,  and  that  the  valley  be  narrow  where 
the  dam  is  to  be  located,  to  avoid  shallow  water  and  expen- 
sive construction.  A  basin  or  valley  with  little  slope  longi- 
tudinally will  provide  a  given  amount  of  storage  with  less 
height  of  dam  than  one  with  a  steep  channel,  and  is  for  this 
reason  preferable.  The  geological  formation  should  be  such 
that  there  may  be  no  loss  of  water  by  leakage  under  or  around 
the  dam,  or  into  another  watershed. 

The  larger  the  drainage  area  above  the  reservoir  the 
greater  the  quantity  of  yield,  and  for  this  reason  the  distance 
of  the  dam  from  the  head  of  this  area  is  important.  But  the 
reservoir  must  be  sufificiently  high  up  the  valley  to  enable 
the  water  to  flow, to  the  point  of  utilization,  or  even  to  furnish 
the  desired  head  of  water  at  this  point.  The  distance  from 
this  point,  also,  and  hence  the  cost  of  the  conduit,  it  is 
desirable  to  make  a  minimum. 

All  of  these  conditions  may  not  exist  at  any  one  point, 
but  each  should  be  given  due  weight  in  choosing  the  location 
of  the  reservoir.  It  may  be  necessary  to  construct  two  or 
more  reservoirs  to  obtain  the  desired  supply,  or  to  carry  the 
water  long  distances.  The  first  consideration  should  be  the 
quality  of  the  supply,  the  next  the  quantity.  A  sufificient 
head  to  avoid  pumping  should  be  aimed  at;  and  this  it  may 
sometimes  be  desirable  to  obtain  by  constructing  two  or  more 
reservoirs  rather  than  by  pumping  from  one  at  a  lower  eleva- 
tion. The  location  of  the  dam  with  reference  to  its  stability 
is  a  matter  of  great  importance;  and  the  distance  away  of 
materials  for  constructing  the  dam  and  convenience  of  trans- 
portation are  important  financial  considerations.  Sound  bed- 
rock at  or  near  the  surface  is  desirable;  or  a  thick  bed  of 
hardpan  or  clay,  if  an  earth  embankment  is  to  be  used. 


1 62  WATER-SUPPLY  ENGINEERING. 

In  deciding  the  exact  location  of  the  dam,  cost  will 
generally  be  the  controlling  consideration.  The  elevation  of 
the  crest  having  been  decided  upon,  that  location  is  then  best 
which  requires  the  least  expense  for  excavation  and  construc- 
tion ;  and  this  is  generally  when  the  least  quantity  of  material 
is  required  for  construction.  To  decide  this  point  an  accurate 
contour-map  should  be  made  of  the  surface  of  the  ground 
and  of  the  rock  or  hardpan  to  which  the  dam  is  to  extend, 
and  the  approximate  quantities  required  for  several  trial 
locations  calculated  ;  unless  one  location  appears  by  inspection 
to  be  undoubtedly  the  best.  In  many  cases  a  straight  dam 
at  the  narrowest  point  is  the  best  location;  but  conditions  of 
topography  are  frequently  met  with  which  make  more 
economcial  a  dam  whose  centre  line  is  curved  up-stream,  or 
contains  an  angle.  A  detour  may  sometimes  be  desirable, 
also,  to  avoid  a  fault  in  the  rock  bottom;  ^nd  a  curve  adds 
to  the  stability  of  a  masonry-dam. 

Art.    49.     Storage-reservoirs:     General    Construc- 
tion. 

The  amount  of  storage  required,  and  consequently  the 
capacity  of  the  storage-reservoir,  has  been  treated  of  in 
Art.  33.  The  relation  between  area  and  depth,  and  the 
general  shape  of  the  reservoir,  must  ordinarily  depend  upon 
the  topography  of  the  country;  but  the  more  regular  the 
shore-line  the  better,  since  small  depressions  in  this  are  apt 
to  cause  stagnation  of  the  water,  and  since  in  general  shallow 
water  and  consequent  danger  from  organic  growths  increase 
with  the  length  of  shore. 

Shallow  water  not  only  encourages  the  growth  of  algae 
and  other  vegetable  organisms  by  admitting  light  and  heat 
to  the  bottom  and  more  polluted  layers  of  water,  but  it  also, 
in  summer,  causes  the  average  temperature  of  the  water  to 


GRAVITY  SYSTEMS.  1 63 

be  higher.  On  the  other  hand  the  deeper  layers  are  apt  to 
become  stagnant  in  summer  (see  Art.  34)  below  a  depth  of 
10  to  20  feet.  The  depth  of  non-stagnation  can  be  increased 
by  increasing  the  exposure  to  winds,  as  by  clearing  the  shores 
of  timber  for  some  distance  back  from  the  reservoir;  but  this 
would  also  increase  the  evaporation,  which  is  largely  affected 
by  wind,  and  the  amount  of  sediment  washed  into  the  reser- 
voir by  storms,  and  is  not  to  be  recommended.  Decrease  in 
depth  also  means  increased  surface  area  and  consequent  loss 
by  evaporation.  A  deep  reservoir  is  hence  advisable  for  all 
reasons  except  the  formation  of  a  stagnant  layer,  which  may 
pollute  the  whole  reservoir  when  the  water  "  turns  over  "  in 
October  or  November.  If  the  reservoir  contains  little  organic 
matter  or  unoxidized  nitrogen,  this  lower  layer  is  not  likely 
to  become  polluted,  however;  and  this  condition  of  water 
should  be  obtained  when  possible. 

It  is  difficult  to  prevent  the  growth  of  large  amounts  of 
plants  and  other  vegetable  organisms  in  water  which  is  less 
than  four  or  five  feet  deep;  and  it  is  therefore  advisable  that 
as  little  as  possible  of  the  reservoir  water  have  less  than  this 
depth  for  any  length  of  time.  This  requires  that  the  shores 
should  all  be  steep  down  to  a  depth  of  five  or  more  feet 
below  the  ordinary  water-surface,  and  that  all  elevations  in 
the  bottom  which  would  cause  shallows  be  removed.  An 
ideal  reservoir  would  be  approximately  oval  in  shape,  with 
vertical  retaining-walls  along  the  shores  reaching  a  depth  of 
ten  feet  or  more,  the  bottom  rapidly  reaching  the  maximum 
depth  of  twenty  or  more  feet,  at  which  depth  it  would  have 
a  uniform  flat  surface.  Paved  slopes  may  be  substituted  for 
vertical  walls  to  save  expense;  and  the  oval  form  can  be  only 
distantly  approximated  in  practice. 

The  prevention  of  pollution  of  water  by  surface  impurities 
has  already  been  alluded  to.  But  it  is  also  necessary  to 
prevent  pollution  of  the  water  while  in  the  reservoir.     This 


164  WATER-SUPPLY  ENGINEERING. 

pollution  may  come  from  the  reservoir  itself  or  reach  the 
reservoir  from  the  outside.  The  first  is  generally  due  to  the 
improper  cleaning  of  the  reservoir  before  filling.  Any  organic 
matter  in  the  bottom  of  the  reservoir  is  slowly  decomposed 
and  the  resulting  nitrogen  often  supports  vast  quantities  of 
algae.  Many  reservoir  sites  have  been  cleared  merely  by 
cutting  down  the  trees  and  bushes,  leaving  stumps,  roots, 
grass,  and  other  vegetable  matter;  but  the  majority  if  not 
all  of  such  reservoirs  for  years  afterward  give  trouble  by  the 
pollution  of  the  water  due  to  the  decomposition  of  this 
matter.  The  "fishy"  taste  so  often  found  in  impounded 
waters  is  generally  due  to  this  false  economy  in  but  partially 
clearing  the  reservoir  site.  All  organic  matter  should  be 
removed  from  a  reservoir  bottom.  Investigations  made  by 
Prof.  Thos.  M.  Drown  in  1893  for  the  Massachusetts  State 
Board  of  Health  seemed  to  show  that  in  ordinary  uncleared 
land  the  proportion  of  organic  matter  in  the  soil  was  greatest 
near  the  surface,  and  below  9  to  1 1  inches  decreased  rapidly, 
being  seldom  more  than  i^  to  2  per  cent  at  a  depth  of  one 
foot,  although  amounting  to  15^  in  some  surface  soil.  Swamp 
land  or  muck  showed  much  larger  percentages  of  organic 
matter.  The  conclusion  reached  was  that  all  soil  containing 
more  than  i^  to  2  per  cent  of  organic  matter  should  be 
removed,  which  generally  involves  taking  off  the  top  12 
inches.  All  stumps  should  of  course  be  removed.  Pockets 
of  muck  should  be  cleared  out;  but  if  these  are  very  deep 
only  the  top  8  or  10  feet  need  be  removed,  and  the  holes 
should  then  be  refilled  with  clean  sand  or  gravel. 

All  buildings  should  of  course  be  removed  from  a  reservoir 
site,  and  all  organic  wastes  deposited  there  by  former  residents ; 
the  privies  in  particular  being  cleaned  out  and  the  soil  for  some 
distance  around  them  being  removed,  the  excavation  being 
then  disinfected  and  refilled  with  clean  gravel  and  sand,  or 
earth  free  from  organic  matter.      Care  should  also  be  taken 


GRA  VI  TVS  VS  TEMS.  1 6  5 

that  the  soil  is  not  polluted  by  the  workmen  upon  the  reser- 
voir; to  prevent  which,  closets  should  be  provided  below  the 
dam  site  and  the  workmen  compelled  to  use  them.  The 
Sodom  Reservoir  included  within  its  boundaries  twenty-one 
dwellings  and  barns,  three  mills  and  two  factories,  besides  six 
miles  of  roads;  and  the  Vyrnwy  Reservoir  (Liverpool  water- 
works) embraced  the  village  of  Llanwddyn,  consisting  of 
about  forty  dwellings,  with  barns,  etc.,  and  a  cemetery. 

It  would  be  quite  desirable  to  provide  a  concrete  or 
similar  artificial  bottom  for  a  storage-reservoir,  but  the  cost 
involved  renders  this  impracticable. 

Pollution  from  outside  the  reservoir  may  be  from  human 
beings  defecating  upon  the  banks  or  swimming  in  the  waters; 
from  organic  matter  deposited  therein  through  malice  or 
ignorance;  and  from  leaves  and  organic  dust  blown  into  the 
water.  (It  is  of  course  assumed  that  no  stables,  piggeries, 
or  out-houses  will  be  permitted  around  the  reservoir.)  No 
picnics,  bathing,  or  loitering  around  the  banks  of  the  reservoir 
should  be  permitted;  to  insure  which  a  watchman  should  be 
constantly  on  hand.  (It  may  be  desirable,  however,  to 
permit  driving  around  the  reservoir.)  To  better  permit 
watching  the  reservoir  banks,  and  also  to  prevent  leaves  from 
falling  into  the  water,  it  is  well  to  clear  all  trees  and  other 
vegetation  from  a  space  25  to  100  feet  wide  all  around  the 
reservoir  banks. 

The  water  entering  the  reservoir  should  bring  as  little 
matter  in  suspension  as  possible.  For  this  reason,  if  the 
stream  have  considerable  volume  and  velocity  it  may  be 
desirable  to  provide  a  settling-basin  at  its  entrance  in  the 
reservoir;  generally  by  constructing  a  submerged  weir  across 
the  reservoir  from  bank  to  bank  near  the  mouth  of  the 
stream. 

The  conduit  must  receive  water  from  the  reservoir  in  such 
a  way  that  there  is  no  loss  by  leakage,  that  the  mouth  of  the 


TOO  WATER-SUPPLY  ENGINEERING. 

conduit  can  be  tightly  closed  if  desired,  that  no  gravel,  sand, 
leaves,  fish,  ice,  or  other  matters  can  enter  it,  and  that  the 
water  can  be  drawn  from  different  elevations  above  the  reser- 
voir bottom  at  pleasure. 

It  must  also  be  possible  to  draw  off  and  waste  the  water 
from  the  bottom  of  the  reservoir  when  this  is  to  be  cleaned 
or  repaired;  or,  as  is  often  desirable,  to  remove  the  bottom 
layers  of  stagnant  water  just  before  the  "  turn-over." 

Art.  50.     Spillways. 

If  the  reservoir  should  be  approximately  full  at  the  time 
of  a  rain-storm,  the  run-off  from  this  would  need  to  overflow 
and  be  wasted.  Provision  for  this  is  one  of  the  most  im- 
portant details  of  reservoir  designing,  and  insufificient  allow- 
ance for  it  has  caused  more  damage  and  loss  of  life  than  all 
other  reservoir  details  combined.  This  waste  water  can  of 
course  be  allowed  to  flow  over  the  whole  length  of  the  dam 
creating  the  reservoir,  but  this  is  not  permissible  in  the  case 
of  an  earthen  dam,  and  requires  a  most  substantial  construc- 
tion along  the  whole  foundation  and  front  of  a  masonry  or 
timber  one.  For  these  reasons  the  waste-water  is  usually 
provided  for  by  a  spillway,  waste-way,  or  waste-weir. 

A  waste-weir  in  the  centre  or  side  of  a  dam  is  frequently 
used,  being  practically  but  a  part  of  the  dam  whose  top  is 
lower  than  that  of  the  remainder  and  whose  construction  is 
more  substantial.  The  waste-water  flows  from  this  to  the  bed 
of  the  original  stream.  A  spillway  is  frequently  provided  in 
the  bed-rock  at  one  end  of  the  dam,  the  rock  being  so  cut 
down  as  to  permit  the  water  to  overflow  at  the  desired  level. 
Where  applicable,  this  method  is  generally  preferable  to  a 
weir.  A  side  spillway  is  practically  a  continuation  of  the 
dam  along  one  side  of  the  reservoir  by  a  low  wall  whose  top 
serves  as  the  weir,  the  waste-water  flowing  along  a  channel 


GRAVITY  SYSTEMS.  1 6/ 

between  this  and  the  ground  outside  the  reservoir.  This 
construction  is  practicable  only  when  rock  is  found  near  the 
spillway  level  along  one  side  of  the  reservoir,  to  serve  as 
foundation  for  the  wall  and  bed  for  the  waste-water  channel. 

In  some  instances  the  spillway  is  entirely  separate  and  at 
some  distance  from  the  dam,  being  placed  in  a  depression  or 
"saddle"  in  the  surrounding  hills,  to  which  the  water  is 
raised  by  the  dam.  A"  low  masonry  waste-weir  will  then 
suffice,  and  all  danger  from  wash  at  the  toe  of  the  dam  be 
avoided,  the  water  being  discharged  into  another  valley. 
This  plan  cannot  often  be  adopted,  but  where  practicable  is 
an  admirable  one. 

The  waste-weir  or  spillway  should  be  constructed  in  the 
most  substantial  manner  to  withstand  the  shock  of  the  over- 
flow from  the  greatest  floods.  Its  top  must  be  designed  to 
receive  the  blows  from,  and  to  pass  over  its  crest,  ice,  logs, 
or  any  other  matter  brought  down  by  the  flood.  It  must, 
without  any  possibility  of  failure  or  of  choking  up,  so  provide 
for  the  passing  of  all  water,  ice,  and  floating  matter  that  the 
water  in  the  reservoir  can  never  under  any  condition  reach 
the  top  of  the  dam. 

The  length  of  a  spillway  and  the  depth  of  water  to  flow 
over  it  demand  careful  consideration.  The  elevation  of  the 
top  of  the  spillway,  and  not  that  of  the  dam,  decides  the 
elevation  of  the  water-surface  in  the  reservoir  and  hence  the 
amount  of  storage  provided.  This  elevation  then  is  the 
starting-point.  The  water  should  never  reach  such  a  level 
that  its  waves  can  rise  above  the  top  of  the  dam,  which  must 
therefore  be  higher  than  the  spillway  by  an  amount  equal  to 
the  greatest  depth  of  water  on  the  spillway  plus  the  greatest 
height  of  waves  possible.  If  the  dam  be  long,  this  additional 
height  will  add  considerably  to  the  expense;  and  to  keep  it 
at  a  minimum,  the  depth  of  water  on  the  spillway  must  be 
decreased  by  increasing  its  length.      But  this  may  mean  an 


l68  WATER-SUPPLY  ENGINEERING. 

increased  cost  due  to  the  spillway,  which  is  often  much  more 
expensive  per  lineal  foot  than  the  rest  of  the  dam.  The 
least  expensive  construction  can  ordinarily  be  ascertained  only 
by  comparing  two  or  more  plans.  The  depth  of  flow  over 
the  spillway  during  heavy  floods  should  not  be  so  shallow  as 
to  permit  of  ice,  logs,  etc.,  stranding  there  and  forming  an 
obstruction.  For  the  same  reason  piers,  posts,  or  other 
obstructions  which  would  be  likely  to  catch  ice,  brush,  or 
other  floating  matter  should  not  be  placed  in  the  spillway. 

The  depth  to  be  allowed  for  waves  will  vary  with  the 
length  of  the  reservoir  and  consequent  sweep  of  wind  possi- 
ble.     Stevenson  gives  the  formula 

7/=z  i.5iZ  +  (2.5  -VZ\ 

in  which  H  is  the  maximum  height  of  wave,  in  feet,  and  L  is 
the  length  of  the  reservoir,  in  miles.  If  the  reservoir  be 
\  mile  long,  this  formula  would  give  2f  feet  as  the  maximum 
height  of  waves;  and  if  2  miles  long,  3^  feet.  Two  feet  is 
the  least  which  should  ever  be  assumed  for  wave  height. 

In  calculating  the  capacity  of  a  spillway — that  is,  the 
maximum  rate  of  run-off  from  any  storm — the  method  out- 
lined in  Art.  32  is  recommended,  rather  than  any  of  the 
formulas.  The  Melzingah  (N.  Y.)  dam,  which  failed  by 
overflowing  in  July  1897,  had  a  spillway  which,  calculating 
by  the  formulas,  was  sufficient  for  its  drainage  area  of  i.i 
square  miles,  but  which  proved  its  practical  insufficiency. 

It  will  generally  be  desirable  to  calculate  the  run-off  from 
maximum  rates  of  precipitation  for  10,  20,  40,  and  60  minutes 
on  the  drainage  area,  if  this  be  small;  and  for  i,  2,  6,  12, 
and  24  hours  if  it  be  large;  and  for  the  whole  area  in  either 
case;  since  the  run-off  from  a  part  of  the  area  due  to  a  short- 
period  rate  of  rainfall  viay  be  greater  than  that  from  the 
whole  due  to  the  lower  rate  of  rainfall  involved.  By  using 
these  few  calculations  to  plot  a  curve  representing  the  run-off 


GRAVITY   SYSTEMS.  169 

due  to  maximum  precipitations  for  different  intervals  of  time, 
the  maximum  rate  of  run-off  may  be  determined. 

Art.  51.     Distributing-reservoirs. 

The  reasons  for  the  use  of  distributing-reservoirs  have 
been  given  in  Art.  47.  Where  these  are  not  used  the 
storage-reservoir  acts  as  a  distributing-reservoir  also. 

The  damming  of  a  valley,  when  one  admitting  of  tliis  is 
favorably  located,  is  the  least  expensive  method  of  forming  a 
distributing-reservoir.  In  most  cases,  however,  such  a  reser- 
voir is  constructed  on  the  top  or  side  of  a  hill  above  and  near 
the  point  of  utilization.  In  such  a  situation  part  or  all  of  the 
sides  of  the  reservoir  are  in  most  cases  partly  in  embankment. 
Stability  and  economy  are  generally  best  obtained  by  locating 
a  reservoir  on  comparatively  level  ground,  thus  avoiding  high 
embankments;  and  in  no  case  should  any  part  of  the  bottom 
of  a  reservoir  be  above  the  original  ground-surface.  The 
location  should  generally  be  as  nearly  as  possible  on  the 
direct  conduit-line  from  the  storage-reservoir  to  the  point  of 
utilization,  and  near  the  latter.  Many  distibuting-reservoirs 
have  been  located  within  the  limits  of  a  city,  as  is  the  case  in 
New  York  and  Philadelphia. 

The  reservoir  capacity  should  be  at  least  equal  to  the 
maximum  consumption  for  three  or  four  days.  It  is  desir- 
able to  have  two  reservoirs,  or  one  divided  by  a  partition- 
wall,  that  each  may  separately  be  emptied  and  cleaned  with- 
out interrupting  the  service.  This  also  permits  the  water  to 
stand  for  three  or  more  days  and  deposit  any  sediment  which 
it  may  contain,  the  other  reservoir  being  used  meantime. 

In  plan  the  reservoir  is  frequently  a  quadrilateral,  with 
rounded  corners  if  earth  embankments  be  used.  But  this 
is  determined  by  economical  considerations,  the  greatest 
capacity  being  obtained  at  tlie  least  expense. 


I/O  WATER-SUPPLY  ENGINEERING. 

Since  it  is  so  much  smaller,  a  distributing-reservoir  can 
generally  be  constructed  more  as  theory  dictates  than  can  a 
storage-reservoir.  For  example,  the  banks  can  all  be  given 
a  steep  slope  and  paved  throughout;  the  reservoir  should  be 
of  a  considerable  depth,  there  being  no  "turn-over"  to 
avoid ;  it  can  be  fenced  in  and  all  pollution  from  outside 
sources  avoided,  being  covered  in  some  cases  to  insure  this 
and  to  preserve  a  low  temperature  as  well  as  to  prevent  the 
growth  of  algae. 

A  distributing-reservoir  is  provided  with  a  conduit  from 
the  storage-reservoir  and  one  to  the  distribution  system,  and 
with  a  waste-pipe  to  permit  emptying  it,  as  well  as  gates  for 
controlling  these.  It  should  be  perfectly  tight  and  stable, 
more  particularly  when  in  the  midst  of  or  near  an  inhabited 
section. 

Art.  52.     Gravity  Supplies  from  Large  Streams. 

The  above  articles  have  considered  the  supply  as  being 
from  surface-water  and  small  streams  only;  but  in  some  cases, 
particularly  in  irrigation-works,  a  gravity  supply  is  obtained 
from  a  stream  of  such  size  that  no  storage  is  necessary,  a 
part  only  of  the  ordinary  and  flood  discharges  being  diverted. 
A  canal  or  flume  leading  from  one  bank  of  the  river  will 
intercept  a  part  of  the  flow;  but  it  is  also  necessary  that 
provision  be  made  for  intercepting  a  large  part  or  all  of  it  in 
time  of  low  water,  for  excluding  gravel  and  the  heavier  sedi- 
ment during  floods,  and  for  drawing  off  a  constant  supply  at 
all  times.  This  ordinarily  requires  a  dam  which  will  retain 
all  the  flow  when  necessary,  but  pass  most  of  it  during  flood; 
and  head-gates  by  which  water  can  be  taken  into  the  conduit 
from  the  bed  of  the  river  during  low  water,  but  from  near 
the  surface  during  floods  when  the  bottom  flow  is  full  of 
heavy  sediment.  There  should  also  be  provision  for  flushing 
out  the  deposit  which  will  collect  behind  the  head-gates  and 


GRAVITY   SYSTEMS.  17 1 

dam,  for  which  purpose  sluices  at  the  bottom  of  the  same  are 
desirable.  It  is  also  necessary  to  provide  that  the  channel, 
particularly  at  low  water,  shall  pass  by  the  end  of  the  conduit, 
and  this  may  require  spur-dams,  and  a  sluice  near  this  point. 
It  is  particularly  necessary  in  works  thus  situated  that  the 
foundations  and  all  portions  of  every  structure  be  of  the 
greatest  strength  and  solidity. 

Art.  53.     Open  Conduits. 

Conduits  between  storage-  and  distributing-reservoirs,  and 
all  conduits  in  irrigation  systems,  may  be  open  and  follow 
the  hydraulic  gradient ;  or  may  be  closed  and  rise  and  fall 
with  the  surface,  being  under  internal  pressure  due  to  their 
distance  below  this  gradient.  Conduits  from  distributing- 
reservoirs,  or  from  storage-reservoirs  on  city  supply  systems 
where  there  are  no  distributing-reservoirs,  must,  for  the  last 
part  of  their  length  at  least,  be  under  pressure. 

The  simplest  form  of  open  conduit  is  a  canal  excavated 
in  the  earth.  To  avoid  loss  by  seepage  this  is  frequently 
lined  with  concrete  or  other  material.  Conduits  are  also 
constructed  of  timber,  or  of  sheet  iron  or  steel,  supported  on 
the  ground  or  on  trestles,  or  of  masonry  resting  on  the 
natural  soil  or  on  solid  embankments.  Open  conduits  are 
carried  across  valleys  and  streams  by  means  of  aqueducts,  and 
through  mountains  by  tunnels.  In  some  Western  works  con- 
duits of  concrete,  stone,  wood,  and  iron,  aqueducts,  tunnels, 
and  pressure  conduits  are  all  found  on  the  same  line. 

A  canal  must  ordinarily  follow  quite  closely  the  surface 
contour  of  the  country  traversed,  having  only  such  fall  as 
will  give  the  water  the  desired  velocity.  This  may,  in  a 
mountainous  country,  lead  to  such  detours  as  to  enormously 
increase  the  length,  cost,  and  head  lost.  Where  a  straight 
course  can  be  obtained,  however,  and  the  ground  is  fairly 
level  laterally  as  well  as  longitudinally,  a  dug  canal  is  gen- 


1/2  WATER-SUPPLY  ENGINEERING. 

erally  the  cheapest.  If  the  general  longitudinal  grade  is 
steeper  than  that  permissible  for  the  canal,  an  occasional  drop 
can  be  made  in  the  latter,  either  as  a  falls  or  as  a  rapids,  or 
the  head  can  be  consumed  by  gratings  or  contractions  in  the 
channel,  wooden  or  masonry  construction  being  used  at  these 
points. 

The  chief  objection  to  canals  is  the  great  loss  by  percola- 
tion, which  has  been  found  in  Utah  to  amount  to  20  inches 
per  day;  and  on  the  Erie  Canal  to  from  35  to  100  cubic  feet 
per  minute  per  mile  of  canal  40  feet  wide,  or  about  3  to  10 
inches  per  day.  The  following  table,  compiled  by  Prof. 
L.  G.  Carpenter  of  the  Colorado  Agricultural  Experiment 
Station,  shows  the  daily  loss  by  seepage  on  various  canals. 

Pleasant  Valley  and  Lake  Canal.  .  .  .  c.66  to        5  feet 

North  Farm  Lateral 0.80  " 

Fort  Morgan  Canal i.oo  to  2.60  " 

Hoover  Ditch i  .00  " 

Greely  No.  3,  special  case .  30.00  " 

"  "        July  20,   1898 18.00  " 

North  Poudre  Lateral 0.6    to  i.oo  " 

Muzza  Canal,  Italy 1.70  " 

Naviglio  Grande 0.80  ** 

Martesana  Canal 1.50  ** 

Centreville  and  Kingsbury  Canals.  .  6.00  ** 

Kings  River  and  Fresno  Canal 0.6     to  1.70  " 

Fresno  Laterals 1.2     to  6.40  '* 

Kern  County  Canals 0.39  to  2.60  ** 

"  "  "     sandy  soil I.OO  to  2. 00  ** 

<■<■  '«  '■'■         "      loam.  .  .  .  0.39  to  1.30  " 

Campine  Canal,  Belgium,  sandy...  .  2.00  to  10.00  '* 

Erie  Canal Q.25  to  0.80  " 

Carpentras  Canal,  France 1.20  " 

Marseilles        "  "      0.40  " 


GJ^A  VITY   S  YSTEMS.  I J I 

A  long  canal  in  earth  may  lose  by  seepage  more  water 
than  it  delivers.  To  remedy  this,  much  can  be  done  by 
admitting  water  heavily  charged  with  clay  in  suspension  and 
permitting  it  to  pass  slowly  through  the  canal.  If  the  water 
intercepted  does  not  carry  clay  or  loam,  or  if  the  canal  must 
be  tight  from  the  beginning,  the  sides  may  be  puddled  if 
materials  for  this  are  at  hand.  If  they  are  not,  or  if  still 
greater  tightness  is  desired,  a  cement  lining  n  ay  b^  given  the 
canal.  This  method  was  adopted  in  the  case  of  one  of  the 
Riverside  Irrigation  Canals.  Or  a  heavier  lining  of  concrete 
or  stone  masonry  may  be  used.      (See  Plate  VIII.) 

Where  an  excavated  canal  is  not  constructed  because  of 
seepage,  or  of  unfitness  of  the  soil,  or  because  the  transverse 
slopes  are  so  steep  as  to  require  a  dangerous  amount  of 
embankment,  but  where  the  contour  can  be  followed,  one  or 
both  walls  of  the  canal  are  sometimes  formed  of  masonry,  the 
bottom  of  the  canal  being  either  bed-rock  or  concrete. 

In  place  of  a  canal  a  conduit  or  flume  of  wood,  iron,  or 
steel  is  often  used,  resting  upon  the  levelled  ground  where 
possible,  but  often  upon  trestles  or  embankments.  These 
can  be  made  practically  tight,  thus  permitting  no  loss  of  water 
except  that  due  to  evaporation.  For  crossing  valleys  at  the 
hydraulic  gradient  trestles  or  aqueducts  are  most  frequently 
used.  (See  Plate  IX.)  When  the  flume  rests  upon  a  level 
bench  cut  into  a  hillside  it  is  called  a  bench-flume.  (See 
Plate  X.)  A  flume  should  never  rest  upon  an  embankment, 
which  is  sure  to  settle  somewhat;  and  a  bench-flume  must 
be  water-tight  if  resting  upon  earth,  as  any  erosion  of  this 
caused  by  leakage  would  be  fatal. 

The  name  aqueduct  is  generally  given  to  a  valley  crossing 
oi  some  magnitude  and  of  substantial  construction,  as  of 
masonry.  High  Bridge,  New  York,  is  an  excellent  example 
of  this. 

The  longer  water  remains  in  an  open  conduit  the  greater 


174  IVATER-SUPPLY   ENGINEERING. 

the  loss  by  evaporation  and  seepage;  for  this  reason,  and  to 
prevent  the  growth  of  weeds  in  earth  channels,  considerable 
velocity  is  desirable;  and  is  necessary  also  if  the  depositing 
of  silt  in  the  canal  is  to  be  prevented.  But  if  the  velocity 
become  too  great  the  earth  is  eroded,  or  the  metal,  wood,  or 
masonry  abraded  by  the  sand  or  gravel  carried.  Also,  since 
velocity  is  obtained  at  the  expense  of  head,  a  high  velocity 
may  lower  too  much  the  level  of  the  canal  or  the  pressure- 
'     head  at  the  point  of  utilization. 

m. 

The  growth  of  weeds  may  ordinarily  be  prevented  by  a 
velocity  of  2  to  3  feet  per  second ;  and  this  velocity  will  also 
prevent  the  deposit  of  such  matter  in  suspension  as  should 
properly  be  let  into  even  an  irrigation-canal.  Light  or 
sandy  soil  is  likely  to  be  eroded  by  a  velocity  of  2  feet  or 
more;  in  firm  loam  or  clay  a  velocity  of  3  feet  is  permissible; 
in  brickwork,  wood,  or  sheet-metal  flumes  a  velocity  of  5  or  6 
feet  may  be  allowed  ;  but  if  the  velocity  exceed  this  a  substan- 
tial construction  of  hard  stone  masonry  should  be  provided. 

The  grades  which  will  give  these  velocities,  in  either  an 
open  or  a  closed  conduit,  depend  upon  the  size,  form  of 
channel,  and  character  of  the  wetted  surface,  and  may  be 
calculated  by  Kutter's  or  some  other  acceptable  formula. 
(See  Chapter  XI.)  For  open  conduits  particularly,  Kutter's 
formula  seems  to  be  the  most  satisfactory. 

The  area  of  cross-section  of  the  canal  must  be  greater 
than  the  quotient  obtained  by  dividing  the  maximum  amount 
to  be  passed  per  second,  in  cubic  feet,  by  the  velocity  of  flow 
in  feet  per  second;  the  banks  being  at  least  12  to  18  inches 
higher  than  the  highest  water-surface.  The  irrigating  season 
lasts  but  about  100  days  in  most  of  our  Western  country,  and 
in  that  time  practically  all  of  the  water  used  must  pass 
through  the  irrigating  canal.  This  is  the  basis  of  the  method 
of  expressing  duty  by  "acres  per  second-foot  ";  that  is,  the 
number  of  acres  which   can  be  irrigated  by  a  continuous  flow 


GRAVITY   SYSTEMS. 


175 


GRAVITY  SYSTEMS. 


177 


GKA  VI T  y   S  YS  TEMS. 


179 


m 


GRAVITY  SYSTEMS.  l8l 

during  the  irrigation  period  of  one  cubic  foot  per  second. 
Sixty  to  one  thousand  acres  is  about  the  range  of  duty,  and 
one  hundred  may  be  taken  as  a  general  average  where  no 
exact  data  are  available.  The  higher  rates  are  found  where 
subsurface  irrigation  is  practised;  being  250  to  500  in  the 
San  Bernardino  (Cal.)  district. 

For  example,  if  30,000  acres  are  to  be  irrigated,  duty  100 
acres,  there  must  be  a  flow  of  300  cubic  feet  per  second  plus 
the  loss  by  evaporation  and  seepage;  and  the  area  of  cross- 
section   of  the   canal,    if   the   velocity  be   3  fe'='t  per  second, 

300  cu.  ft.  -\-  per  cent  of  loss 
must  be 7- ,  or  100  square  feet  plus 

the  per  cent  of  loss. 

Another  method  of  calculating  the  flow  in  irrigating- 
canals  is  to  divide  the  total  mean  annual  yield,  less  the 
evaporation  and  seepage  from  the  reservoir,  by  60  X  60  X 
24  X  100,  or  8,640,000,  the  number  of  seconds  in  100  days; 
assuming  that  all  of  the  yield  will  be  used  for  irrigation, 
which  is  naturally  the  condition  aimed  at. 

In  calculating  the  areas  of  canals  for  city  supply,  recogni- 
tion must  be  taken  of  the  fact  that  the  consumption  is  not 
uniform  throughout  the  year,  but  may  be  25  to  50  per  cent 
greater  than  the  average  for  one  or  even  several  days  at  a 
time,  particularly  in  the  summer,  when  the  evaporation  and 
seepage  also  are  greater.  The  amount  designed  to  be  carried 
by  the  canal  will  be  based  upon  these  conditions,  being  at 
least  50^  greater  than  the  average  daily  consumption,  aside 
from  the  evaporation  loss. 

In  case  more  water  were  admitted  to  an  open  conduit 
than  was  being  taken  at  the  lower  end,  the  banks  or  sides  of 
the  conduit  would  be  overflowed,  which  would  in  most  cases 
be  disastrous.  To  prevent  this  the  surplus  water  is  provided 
for  by  specially  constructed  overflows,  called  waste-weirs  or 
waste-ways,  placed  at  intervals  along  the  line. 


1 82 


WATER-SUPPLY  ENGINEERING. 


In  some  cases  no  artificial  conduit  is  constructed  below 
the  storage-reservoir,  which  is  used  as  a  regulator  of  flow 
only,  but  the  discharge  is  conducted  in  the  original  channel 
of  the  stream  to  a  distributing-reservoir  or  intake. 

The  lengths,  dimensions,  and  carrying  capacities  of 
several  American  canals  are  given  below. 

Table  No.    44. 

some  great   irrigation  canals. 

[(From  Wilson's  Manual  of  Irrigation  Engineering.) 


to 

u    • 

^•d 

v 

oj-o 

CJ^   4> 

a -a 

s 

a 

V 

Name  of  Canal. 

Locality. 

rt  M  o 

t  6< 

c 

Grade. 

[1. 

Xi 

a 
u 

to  ^:;? 

0  0> 

< 

►J 
150 

U 

n 

Q 
7 

u 
$  5.00 

u 

Bear  River  Canal. . 

Utah 

200,000 

1000 

I  in  5280 

50 

$125 

Idaho    Mining^  and 

Irrig.  Co.  Canal.. 

Idaho 

350,000 

70 

2585 

I  in  2640 

40 

10 

2.  16 

190 

Pecos  Canal 

N.  Mexico 

200,000 

75 

1 100 

I  in  6707 

45 

6 

5.00 

690 

Turlock    "     

California 

176,000 

93 

1500 

I  in  5280 

70 

7-5 

14.50 

730 

King's    River    and 

SanJoaquinCanal 

** 

90,000 

67 

600 

I  in  5280 

32 

4-5 

7.18 

277 

Calloway  Canal.... 

'* 

80,000 

32 

700 

I  in  6600 

80 

3-5 

10.00 

7iOv 

Arizona          "     .... 

Arizona 

60,000 

41 

1000 

I  in  2640 

36 

752 

10.00 

700 

Highline        "     .... 

Colorado 

90,000 

70 

1184 

I  in  3000 

40 

7 

13.00 

600 

Del  Norte     "    .. .. 

200,000 

50 

2400 

I  in  2112 

65 

5-5 

Art.  54.     Closed  Conduits. 

Open  conduits  are  seldom  used  on  city  water-supply 
systems,  because  of  the  danger  of  pollution,  loss  by  evapora- 
tion, and  variation  of  temperature.  Closed  conduits  are 
hence  provided,  being  generally  made  of  water-tight  construc- 
tion. Should  such  a  conduit  fall  below  the  hydraulic  gradient 
it  would  receive  internal  pressure  and  must  be  of  a  construc- 
tion to  resist  this.  Masonry  conduits  can  do  so  to  but  a  very 
limited  extent,  and  are  hence  adapted  to  those  locations  only 
which  follow  exactly  along  the  hydraulic  gradient.  Such 
location  generally  requires  considerable  cutting,  tunnelling, 
embankments,  trestles  or  masonry  bridges,  and  other  expen- 
sive work*  and  for  this  reason  metal  or  wooden  conduits  able 


GJiAVITV  SYSTEMS. 


18- 


O    6 


<  a 


GRAVITY   SYSTEMS.  1 85 

to  resist  internal  pressure  are  ordinarily  employed  where 
possible.  Where  the  amount  of  water  is  very  considerable 
a  trestle  or  even  a  masonry  aqueduct  may,  however,  be 
cheaper  than  a  pressure  conduit  which  rests  upon  or  in  the 
surface  at  all  points.  A  masonry  conduit  is  in  some  cases 
made  to  resist  internal  pressure  by  constructing  it  as  the  lining 
of  a  tunnel  in  rock,  the  pressure  bein^  received  and  resisted 
by  the  rock;  an  illustration  of  which  is  the  new  Croton 
Aqueduct. 

On  many  irrigation-works  open  aqueducts  are  used  for 
surface  conduits;  but  for  crossing  valleys  a  pressure  conduit 
following  the  surface  is  substituted.  Such  a  conduit,  of 
wood-stave  pipe,  is  shown  in  Plate  XI.  The  same  construc- 
tion is  of  course  adapted  to  city  water-supply  systems. 
The  majority  of  pressure  conduits  for  these  are  now  con- 
structed of  iron  or  steel  plates  for  the  larger,  and  cast  iron  for 
the  smaller,  sizes.  Bored  logs,  indurated  wood-pulp,  and 
cement-lined  sheet-iron  pipes  are  used  for  small  conduits  in 
some  plants.  The  first  pipes  used  in  this  country  were  of 
bored  logs,  and  spruce-log  pipes  eighty-five  years  old  have 
been  found  in  good  condition. 

When  closed  conduits  are  not  under  pressure  their  size 
and  grade  are  calculated  as  in  the  case  of  open  ones;  and 
overflows  or  waste-weirs  are  similarly  provided.  When  under 
pressure  they  must  always  flow  full,  and  the  formulas  for  flow 
in  pipes  are  applied.  No  waste-weirs  are  then  necessary 
except  at  the  head-works;  but  flushing-out  gates  should  be 
provided  at  the  low  points  for  removing  sand  and  other 
deposits. 

The  pressure  to  be  resisted  by  the  tensile  strength  of  the 
walls  of  the  conduit  is  the  hydraulic  pressure  due  to  the 
difference  in  elevation  of  the  conduit  and  of  the  water  in  the 
open  conduit  or  reservoir  at  its  head.  This  pressure  is  not 
attained  when  the  water  is  flowing,  but   only  when  a  gate  at 


1 86 


WA  7'ER-SUPPL  Y  ENGINEERING. 


the  lower  end  of  the  pressure  conduit  is  closed.  When  flow- 
ing, the  pressure  head  equals  the  vertical  distance  between 
the  conduit  and  the  hydraulic  gradient  (see  Art.  63),  and 
this  is  the  maximum  pressure  to  be  provided  for  if  there  be 
no  gate  at  the  lower  end  of  the  pressure  conduit,  or  if  an 
overflow  be  provided  there  at  the  level  of  the  hydraulic 
gradient. 

Both  wood-stave  and  riveted-steel  pipes  have  been  con- 
structed 72  inches  in  diameter,  and  may  be  made  yet  larger. 
Rock  tunnels  can  be  made  of  any  size.  That  on  the  Croton 
Aqueduct  has  an  area  of  about  1 18  square  feet,  or  a  diameter 
of  12  feet  3  inches. 

Table   No.  45. 

SOME    CLOSED    CONDUITS. 


Location. 


Nashua,  Boston 

Sudbury,        "      

Croton,  New  York  ;   Old 
Croton,  New  York  ;   New 

Baltimore,  Md 

Denver,  Colo 

Caldwell,    Idaho 

Bear  Valley,  Cal 

Ogden,  Utah 

Newark,  N.  J 

Rochester,  N.  Y j 

Coolgardie,  Australia... 


Material 


Masonry 


Wood 


Steel 


plate 


Cast  iron 
Steel  plate 


Dimensions, 
Inches. 


126  X 
108  X 

89  X 
147  di 
144 

30 

54 

52 

72 

72 

43 

60 

30 

30 


138 
92 

101.5 
am. 


7.0 
15-9 


29.63 
7.0 

iS.oo 
o.  13 
0.41 
5  10 
0.87 

21.00 
0.30 

20. 
328.0 


> 


6± 

3 

2.218 

30 


8.75 
8. 75 
50 


1.9 


Gravity 


Pressure 


Art.  55.     Location  of  Conduits. 

The  location  of  conduits  when  the  loss  of  a  few  feet  of 
head  is  not  important  is  largely  a  matter  of  economy.  When 
every  available  foot  of  head  must  be  preserved,  however,  the 
alignment  must  be  approximately  straight  and  the  grade  as 


GRAVITY  SYSTEMS.  1 87 

light  as  will  give  the  desired  velocity.  To  avoid  excessive 
evaporation  at  low  velocities,  and  to  permit  following  the 
irregularities  of  surface  in  an  air-line  location,  closed  conduits, 
in  many  or  most  places  under  pressure,  are  used.  There 
may  be  locations  where  the  loss  of  head  in  passing  around  a 
basin  or  pocket  will  be  less  than  in  going  directly  across  it 
with  a  deep  loop  or  inverted  siphon.  A  siphon  proper  is  to 
be  avoided  where  possible,  although  a  number  of  these  are  in 
use. 

If  the  question  is  one  of  cost  only,  a  more  circuitous  line 
is  frequently  preferable.  Although  longer,  it  may  avoid  deep 
cuts  and  tunnels,  may  be  open  most  of  its  length,  may  have 
considerable  fall  and  hence  smaller  cross-section,  and  deep 
inverted  siphons,  calling  for  strong,  high-pressure  conduits, 
may  be  avoided.  In  many  instances,  however,  deep  cuts, 
tunnels,  or  inverted  siphons  may  be  the  less  expensive. 
Estimates  of  cost  for  different  routes  must  generally  be  made 
for  each  section  to  determine  the  most  desirable  location. 

Sharp  curves  should  be  avoided,  since  they  cause  loss  of 
head  and  erosion  of  the  outer  banks  of  canals.  In  general 
the  minimum  radius  of  curvature  of  the  inner  side  of  a  con- 
duit should  be  about  twice  the  product  of  the  depth  of  water 
and  the  velocity  of  flow  in  feet  per  second. 

Streams  should  always  be  crossed  at  a  safe  distance 
beneath  their  beds  or  above  their  highest  flood-lines. 

Swamps  and  other  soils  affording  poor  foundations  should 
be  avoided  if  possible;  if  not,  artificial  foundations  must  be 
carried  down  to  rock  or  firm  soil. 

Art.  56.     Distribution  Systems:  Irrigation. 

Water  which  has  been  impounded  and  brought  to  the 
borders  of  an  irrigation  district  must  still  be  distributed  to  a 
large  number  of   farms  throughout  this  district,   and  to   all 


158  WATER-SUPPLY  ENGINEERING. 

parts  of  each  farm.  This  is  generally  accomplished  by  canals 
or  flumes,  but  in  some  cases  by  pipes.  As  the  limits  of  the 
district  are  approached  the  water  to  be  carried  becomes  less 
and  the  canals  or  pipes  smaller;  the  last  length  carrying  but 
enough  water  to  irrigate  one  farm  in  the  time  allowed  for  its 
use.  From  the  canals  water  is  usually  diverted  into  smaller 
ditches,  and  in  these  led  to  all  parts  of  each  farm.  From 
pipes  the  water  is  led  through  smaller  pipes  to  hydrants, 
which  discharge  the  water  upon  the  ground  directly  or 
through  a  hose.  For  subsurface  irrigation  underground 
open-jointed  pipes  are  used,  fed  from  either  canal  or  pipe 
distributary. 

Irrigation  is  not  continuous  on  any  one  farm,  but  water  is 
applied  from  two  to  ten  times  each  season,  for  periods  of 
from  3  to  15  hours  each;  such  application  being  called  a 
service.  The  times  of  service  for  each  farm  are  fixed  before- 
hand by  the  district  manager.  Thus  each  farm  draws  water 
from  the  canal  for  but  10  to  40  hours  in  a  season  of  100  to 
120  days,  or  ^\j^  to  ^^  01  the  time.  Hence  a  distributor 
which  will  carry  but  sufficient  water  to  irrigate  one  farm 
during  the  time  of  its  service  periods  may  still  serve  72  to 
240  of  such  farms,  which  rotate  in  their  services. 

Distributaries  should,  where  possible,  follow  natural 
ridges  or  elevated  ground,  that  the  water  may  flow  by  gravity 
to  all  parts  of  the  territory  on  either  side.  Each  will  then 
serve  the  land  to  the  bottom  of  its  slope  on  either  side,  and 
should  be  designed  of  corresponding  capacity.  Small  dis- 
tributaries, where  they  can  follow  the  surface  contours,  are 
generally  ordinary  ditches  in  excavation  and  embankment, 
the  bottom  being  kept  at  or  a  little  below  the  original  sur- 
face; where  they  must  rise  above  the  surface  for  a  short  dis- 
tance wooden  box-flumes  are  used.  The  larger  distributaries 
are  sometimes  lined  with  cement  or  concrete,  the  smaller 
with  split  clay  pipes,  where  water  is  scarce  and  valuable.      If 


GRAVITY  SYSTEMS.  1 89 

the  natural  fall  of  the  surface  gives  too  great  velocity,  the 
distributaries  are  built  on  a  flatter  grade,  and  wooden  chutes 
and  falls  are  introduced  at  intervals. 

As  far  as  possible  distributaries  should  be  located  at 
uniform  distances  apart.  They  should  be  as  few  and  large 
as  possible,  since  this  tends  to  reduce  the  losses  by  evapora- 
tion and  seepage,  and  the  expense  of  maintenance. 

Water  is  usually  diverted  from  the  main  to  the  lateral 
distributaries  by  stop-gates  or  other  checks  in  the  main,  and 
tke  amount  admitted  is  regulated  by  a  suitable  gate  or  orifice 
in  the  mouth  of  the  lateral.  The  amount  discharged  from  a 
distributary  to  an  irrigating  farm  is  usually  measured  by  the 
size  of  and  head  above  an  orifice  through  which  it  passes, 
and  the  duration  of  flow.  The  quantity  is  ordinarily  expressed 
in  "  miner's  inches"  in  the  West,  but  second-feet  is  a  unit 
more  desirable  for  many  reasons.  The  miner's  inch  is  a 
variable  quantity,  being  the  same  in  no  two  States.  In 
California  it  is  about  equal  to  -^-^  of  a  second-foot,  in  Colorado 
to  3J5;  while  in  some  States  it  is  not  a  constant,  but  varies 
slightly  with  the  conditions  of  flow  or  the  amount  measured. 

Art.  57.     Distribution  Systems:  City  Supplies. 

The  distributing  system  of  a  city  supply  is  always  com- 
posed of  pressure-pipes.  The  pressure  varies,  in  this  country, 
between  10  and  200  pounds,  with  perhaps  exceptional  cases 
outside  of  these  limits.  The  static  pressure  in  any  part  of  a 
system  fed  by  reservoir  is  that  due  to  the  difference  in  eleva- 
tion of  such  point  and  the  level  of  water  in  the  distributing- 
reservoir.  The  pressure,  in  pounds  per  square  inch,  equals 
0.434  times  this  difference  of  elevation,  in  feet.  Since  there 
will  or  may  be  times  when  no  water  is  being  consumed,  all 
portions  of  a  distribution  system  must  be  designed  to  with- 
stand the  static  pressure. 


190  WATER-SUPPLY  ENGINEERING. 

The  two  chief  objects  of  a  city  water-supply  system  are: 
to  furnish  water  for  domestic,  manufacturing,  and  similar 
purposes;  and  to  afford  fire-protection.  Use  is  also  made  of 
it  in  sprinkling  streets  and  lawns,  flushing  sewers,  etc.  For 
these  purposes  the  distribution  system  should  reach  every 
building,  and  permit  of  placing  fire-hydrants  at  distances 
apart  of  not  more  than  500  feet  in  all  occupied  streets.  The 
filling  of  sprinkling-carts,  supplying  of  fountains,  and  flushing 
of  sewers  must  also  be  provided  for. 

The  pipes  of  a  system  must  not  only  reach  all  these 
points,  but  they  should  be  of  such  size  that  the  required  rates 
of  flow  may  be  obtained  at  any  point.  It  is  desirable  that 
the  pressure  be  such  at  every  fire-hydrant  that  a  stream 
through  400  or  500  feet  of  fire-hose  may  be  thrown  to  the 
top  of  the  highest  building;  but  this  is  not  always  possible, 
especially  where  the  buildings  are  excessively  high. 

An  additional  requirement  is  that  the  pipes  and  attached 
appurtenances  be  amply  capable  of  withstanding  the  greatest 
pressure  to  be  brought  upon  them. 

It  is  desirable  that  all  parts  of  the  system  be  durable, 
requiring  to  be  renewed  only  at  long  intervals  of  time.  Also 
that  it  be  so  arranged  that  repairs,  alterations,  or  renewals 
may  be  made,  or  breaks  occur,  at  any  point  without  interfer- 
ing with  the  service  at  any  other  point.  All  parts  of  the 
system  should  be  easily  located  and  accessible. 

It  is  especially  desirable  that  the  quality  of  the  water  be 
not  impaired  by  any  part  or  condition  of  the  system ;  and 
that  there  be  no  waste  or  leakage  at  unknown  or  inaccessible 
points. 

The  reaching  of  all  buildings  usually  requires  that  a  pipe 
pass  along  one  side  of  every  lot.  This  does  not  always 
necessitate  passing  through  each  street,  since  in  sections  of 
many  cities  all  buildings  face  upon  one  set  of  parallel  streets, 
while  those  crossing  these  pass  but  the  sides  of  corner  lots; 


GRAVITY   SYSTEMS.  ■  I9I 

in  which  case  pipes  upon  the  main  streets  only  will  pass  all 
houses.  In  such  sections  of  a  city  the  lengths  of  cross-streets 
included  between  the  main  streets  seldom  exceed  300  ^o  400 
feet,  and  if  fire-hydrants  be  placed  at  the  corners  no  inter- 
mediate ones  on  the  cross-streets,  and  hence  no  pipes,  will  be 
necessary.  The  filling  of  sprinkling-carts  and  providing  for 
sewer-flushing  and  fountains  will  seldom  require  any  pipes 
not  demanded  by  the  above  considerations. 

The  arranging  of  the  system  to  provide  for  restricting  the 
interruption  of  service  consequent  upon  repairs  and  breaks 
demands  a  means  of  cutting  off  any  small  section  of  it  from 
the  rest  of  the  system.  The  smaller  the  section  cut  off  the 
less  the  inconvenience  caused.  It  is  desirable  that  such 
cutting  off  may  be  effected  quickly  in  case  of  a  break  or  other 
accident.  This  is  generally  attained  by  inserting  stop-gates 
or  valves  in  the  lines  of  the  pipes.  These  can  be  placed  at 
any  desired  distance  apart,  but  one  on  each  line  at  each 
corner  is  probably  as  close  as  it  is  generally  desirable  to  place 
them.  When  so  located  not  more  than  four  gates  need  to 
be  closed  to  cut  out  any  short  section  less  than  one  block 
long.  Thus,  in  Fig.  18,  a  break  at  5  would  require  the  clos- 
ing of  gates  at  A,  B,  C,  and  H  to  exclude  all  water  from  that 
point  while  making  repairs.  The  point  T  can  be  cut  out  by 
closing  /and,y;  and  U,  by  closing  C,  D,  and  E.  In  neither 
of  these  cases  will  any  section  except  that  between  the  gates 
named  be  deprived  of  water.  If  gates  be  placed  on  only 
every  other  corner  on  each  line,  twice  the  length  of  pipe  will 
be  put  out  of  service  by  breaks  or  repairs. 

Of  the  pipes  and  conduits  which  are  usually  placed  in  a 
street,  all  cannot  occupy  the  centre.  For  several  reasons  it 
is  generally  desirable  that  the  sewers  occupy  this  position ; 
and  the  water-pipe  must  therefore  be  on  one  side  of  the 
centre.  Which  side  is  not  a  matter  of  very  great  importance; 
but  the  north  side  offers  the  advantage  of  being  warmer,  and 


192 


WATER-SUrPLY  ENGINEERING. 


hence  giving  less  opportunity  for  the  freezing  of  the  pipes. 
The  same  side  of  all  streets  throughout  the  city  should   be 


Fig.   18. — Location  of  Mains  and  Valves. 

used  for  the  water-pipe,  however — as  the  north  and  west  sides 
— to  facilitate  ready  location. 

In  order  that  the  pipe  may  be  quickly  and  readily  located, 
it  should  be  placed  at  a  uniform  distance  from  some  fixed  line 
of  the  street  in  all  parts  of  the  system.      This  line  may  be 


GRAVITY  SYSTEMS.  1 93 

the  centre  of  the  street,  the  curbing,  or  the  property-line. 
The  use  of  the  centre-line  requires  that  this  be  first  located, 
thus  more  than  doubling  the  time  and  labor  required. 
When  streets  and  sidewalks  are  of  different  widths,  the  use 
of  a  constant  distance  from  either  curb  or  property-line  is 
impossible  or  inadvisable.  The  author  has  adopted,  as  a 
satisfactory  method,  a  distance  from  the  property-line  of  such 
multiple  of  five  feet  as  will  bring  the  pipe  between  five  and 
ten  feet  from  the  curb.  The  property-line,  usually  indicated 
by  a  fence  or  house-front,  is  easily  found,  and  there  is  little 
danger  of  using  the  wrong  multiple  of  five  for  the  distance. 
For  instance,  in  a  6o-foot  street  with  i2-foot  sidewalks  the 
pipe  would  be  located  20  feet  from  the  property-line. 

The  hasty  location  of  a  gate  is  often  more  important  than 
that  of  the  pipe — as  in  case  of  a  break,  when  the  flow  in  that 
section  must  be  stopped  immediately  to  prevent  further 
damage.  In  many  systems  the  memory  of  the  superintendent 
or  the  maps  in  the  ofifice  must  be  consulted  before  a  gate  can 
be  located,  and  if  either  or  both  of  these  be  temporarily  lost 
great  delay  and  damage  may  result.  This  can  easily  be 
avoided  by  placing  the  gates  systematically,  as  in  line  with 
the  curbing,  in  the  middle  of  the  cross-walk,  or  in  range  with 
the  property-line.  The  last  named  offers  the  most  ready 
method  of  location  in  winter,  when  the  curb  and  cross-walk 
are  hidden  under  the  snow.  The  gates  should  be  on  a 
uniform  side  of  the  corner,  also.  In  Fig,  18,  all  pipes  being 
upon  the  north  and  west  sides  of  the  streets,  and  all  gates  on 
the  northwest  corners  and  in  range  with  and  at  a  known  dis- 
tance from  the  property-  or  fence-lines,  their  exact  location 
can  be  found  in  a  few  seconds. 

Post  fire-hydrants — that  is,  those  which  stand  above  the 
ground  two  to  four  feet — can  readily  be  found  if  their 
approximate  location  is  known.  (In  winter,  snow  should 
never  be  allowed  to  cover  them,  but  they  should   be  kept 


194  WATER-SUPPLY   ENGINEERING. 

shovelled  out  and  ready  for  instant  use.)  Flush-hydrants, 
which  are  flush  with  the  street-paving,  should  be  located 
uniformly  in  a  manner  similar  to  that  used  for  gates.  Any 
other  underground  fixtures  will  be  so  few  in  number  that  the 
location  of  each  can  generally  be  fixed  in  the  memory  as  well 
as  recorded  in  the  office. 

The  prevention  of  waste  and  leakage,  and  the  withstand- 
ing of  pressure,  depend  upon  the  selection  of  suitable  mate- 
rial and  obtaining  of  careful  workmanship.  The  pressure  to 
be  provided  for  at  any  point  is  treated  of  in  Chapter  XL 

The  maintenance  of  the  quality  of  the  water  requires  that 
all  portions  of  the  pipe,  gates,  and  other  appurtenances  which 
come  into  contact  with  the  water  shall  give  to  it  no  taste  or 
odor  or  objectionable  soluble  matter.  Some  coatings  used 
on  iron  pipes  and  gates  give  a  tarry  taste  to  the  water  for  a 
short  time,  but  this  is  not  injurious  and  soon  passes  away. 
The  most  frequent  violation  of  this  principle  is  in  the  use  of 
lead  or  lead-lined  pipes,  this  metal  being  soluble  in  some 
waters.  In  general,  soft  waters  dissolve  lead  and  temporarily 
hard  waters  do  not.  The  action  upon  a  given  lead  surface 
diminishes  with  time,  but  may  be  so  considerable  as  to  cause 
lead  poisoning  in  consumers.  The  only  sure  method  of 
determining  whether  a  given  water  attacks  lead  is  to  test  it 
by  actual  contact  with  a  bright  lead  surface  for  several  days. 
Zinc  also  is  soluble  in  some  waters,  but  is  not  so  dangerous 
to  the  human  system  as  is  lead.  For  waters  which  attack 
these  metals,  service-pipes  of  iron  lined  with  tin  or  cement 
are  recommended. 

If  the  water  contain  any  organic  matter,  its  stagnation  in 
a  pipe  deprived  of  light  and  air  is  likely  to  cause  offensive 
decomposition,  although  this  matter  might  have  been  of  a 
harmless  nature.  Stagnation  also  favors  the  deposit  in  the 
pipes  of  any  mineral  matters  carried  in  suspension.  It  is 
therefore  desirable  that  the  water  in  all  parts  of  a  distribution 


GRAVITY  SYSTEMS.  I95 

system  be  kept  in  motion  as  much  as  possible.  If  but  one 
house  be  located  in  the  southwest  block  of  Fig.  18,  as  at  W, 
the  water  between  it  and  the  dead-end,  V,  will  lie  stagnant, 
and  if  it  become  putrid  may  contaminate  the  water  enter- 
ing IV.  Or  if  no  water  be  used  at  W  for  some  time,  the  first 
to  be  drawn  may  be  unfit  for  use.  Another  objection  to  the 
dead-end  is  that  water  drawn  from  the  fire-hydrant  ]^  must 
all  pass  through  the  pipe  VM;  but  if  pipe  be  laid  along  the 
dotted  lines,  connecting  with  the  system  at  V,  X,  and  F, 
water  will  reach  the  hydrant  from  both  directions,  and  the 
velocity  of  flow  and  friction-head  in  J/ F  will  be  reduced  and 
the  discharge  from  the  hydrant  increased.  For  both  these 
reasons  dead-ends  are  to  be  avoided  where  possible.  When 
they  cannot  be,  a  fire-hydrant  or  other  method  of  flushing 
out  the  "dead  "  water  should  be  provided  at  each  dead-end, 
and  opened  at  intervals  throughout  the  year. 

It  is  evident  that,  with  a  system  of  pipes  in  which  the 
water  may  circulate  freely  in  all  directions,  the  proper  deter- 
mination of  sizes  is  a  matter  of  some  difficulty,  since  water 
will  reach  any  point  not  in  a  dead-end  through  a  number  of 
pipes,  and  not  through  one  alone.  This  determination  will 
be  considered  in  Art.  94,  and  the  material  and  strength  of 
pipes  in  the  same  article. 

If  there  be  considerable  difference  of  elevation  in  different 
sections  of  a  city,  a  desirable  pressure-head  in  the  upper  ones 
will  occasion  an  excessive  head  in  the  lower,  if  they  be  con- 
nected. This  difficulty  is  overcome  by  dividing  the  city  into 
two  or  more  districts,  each  with  its  own  system,  and  generally 
its  own  distributing-reservoir.  In  a  few  cases  the  "  low 
service  "  system  receives  its  supply  from  the  "  high  service," 
but  a  pressure-regulator  is  placed  at  the  junction,  which  cuts 
off  the  supply  when  the  pressure  in  the  lower  system  exceeds 
a  certain   amount.     The  great   damage  which    might   result 


196  WATER-SUPPLY  ENGINEERING. 

should  the  regulator  fail  to  either  open  or  close  when  intended 
makes  this  plan  a  risky  one,  however. 

The  city  of  Providence,  R.  I.,  has  constructed  in  the  low- 
service  district  a  supplementary  fire  system  of  mains  of  extra 
strength,  which  it  has  connected  with  its  high  service,  and 
thus  obtains  high  pressure  for  fire  service  in  the  lower  and 
business  part  of  the  city. 

QUERIES. 

15.  The  Sweetwater  Reservoir  is  connected  with  the  irrigation- 
fields  by  a  closed  conduit.  Had  this  been  an  open  canal  in  earth, 
10  feet  wide  and  10  miles  long,  what  percentage  of  the  supply  would 
have  been  lost  by  evaporation  and  seepage,  placing  the  last  at 
9  inches  per  day  ?      (See  page  127.) 

16.  Calculate  the  area  of  cross-section  of  the  above  canal,  if  the 
velocity  be  3  feet  per  second  ;  all  the  available  mean  supply  being 
used  in  120  days. 


CHAPTER    X. 

PUMPING    SYSTEMS. 

Art,  58.     Where  Required. 

Where  the  impounding  reservoir,  stream,  or  lake  form- 
ing the  source  of  supply  is  at  a  lower  elevation  than  the  land 
to  be  irrigated  or  the  highest  building  to  be  supplied  thereby, 
the  water  must  be  raised  to  such  elevation.  Even  though 
the  reservoir  be  at  a  greater  elevation,  if  the  excess  is  not 
sufficient  to  overcome  the  friction  in  the  conduit,  pumping 
must  be  resorted  to.  Ground-waters  are  occasionally  found 
at  such  elevations  that  pumping  is  unnecessary;  but  in  most 
cases  they  must  be  raised  from  beneath  the  ground-surface, 
in  some  instances  several  hundred  feet  even.  As  a  general 
statement,  subject  to  many  exceptions,  however,  impounded 
surface-supplies  do  not  need  pumping;  while  river,  lake,  and 
ground-waters  do.  The  majority  of  exceptions  to  the  latter 
statement  are  found  among  irrigation  systems,  where  the 
water  is  not  required  above  the  surface  of  the  ground. 

Since  a  pump,  like  any  mechanism,  is  subject  to  interrup- 
tion or  discontinuance  due  to  breaks  or  other  causes,  while 
gravity  never  ceases  to  act,  pumping  is  to  be  avoided  where 
possible.  If  a  ridge  somewhat  higher  than  the  hydraulic 
gradient  of  a  gravity  conduit  interpose  in  the  line  of  this,  it 
will  generally  be  better  to  tunnel  it  than  to  pump  over  the 
summit.  If  such  a  tunnel  cost  less  than  a  pumping  plant 
plus    the    capitalization    of    all    expenses    of    pumping    and 

197 


198  WATER-SUPPLY  ENGINES  PING. 

renewal,    it    offers    the     more    economical     solution     of    the 
problem,  as  well  as  the  more  desirable. 

Art.  59.     General  Design. 

The  water  which  is  raised  by  a  pumping  plant  must  pass 
through  a  pressure-pipe,  or  pumping-main,  either  directly  to 
the  point  of  utilization,  or  to  a  storage-  or  distributing-reser- 
voir, or  to  a  standpipe.  The  first  is  called  the  direct-pump- 
ing system.  This  requires,  aside  from  the  distribution 
system,  the  construction  necessary  to  conduct  the  water  to 
the  pump;  the  pumping  plant  and  building  in  which  it  is 
housed ;  and  the  pumping-main.  The  pressure  in  a  city 
supply,  with  direct  pumping,  depends  upon  that  in  the  pump- 
cylinders,  and  when  the  pumps  cease  working  the  pressure 
falls  to  zero  or  to  that  of  a  gravity  system.  If  the  pump  in 
such  a  plant  breaks  down,  the  supply  is  immediately  cut  off, 
unless  a  duplicate  plant  be  provided;  which  is  always  desir- 
able, but  most  so  in  a  direct-pumping  system.  This  system 
is  not  advised  for  city  supplies,  but  is  generally  satisfactory 
for  irrigation  purposes. 

In  pumping  to  a  reservoir,  or  an  indirect-pumping  system^ 
there  is  required  a  pumping-main,  a  reservoir,  and  a  conduit 
from  this  to  the  point  of  utilization.  In  some  plants  the 
pumping-main  passes  through  and  forms  a  part  of  the  dis- 
tribution system,  and  also  acts  as  the  conduit  between  this 
and  the  reservoir;  the  water  passing  directly  to  the  distribu- 
tion system,  but  being  augmented  by  that  from  the  reservoir 
when  the  amount  pumped  is  less  than  the  consumption;  and 
the  surplus,  when  it  is  greater  than  the  consumption,  passing 
to  the  reservoir.      Such  a  system  is  called  a  direct-indirect. 

In  the  direct-pumping  system  the  pressure  in  a  city  supply 
is  made  to  vary  constantly  by  variations  in  the  rate  of  con- 
sumption  which   the   rate   of   pumping   cannot  be   made   ta 


PUMPING    SYSTEMS.  1 99 

follow  exactly.  Moreover  when,  as  in  the  case  of  fire,  a 
greater  demand  is  unexpectedly  made  upon  the  supply,  the 
pumps  may  not  for  some  time  be  able  to  meet  it  with 
increased  delivery.  For  these  reasons  the  indirect  or  direct- 
indirect  system  is  preferable. 

When,  for  want  of  an  elevated  site  or  other  reason,  a 
reservoir  cannot  be  had,  a  water-column  is  frequently  intro- 
duced to  equalize  the  pressure;  and  if  it  be  given  considerable 
size  of  cross-section  it  will  serve  to  temporarily  supply  a 
deficiency  in  pump-delivery.  Such  a  water-column  generally 
takes  the  form  of  a  standpipe  or  water-tank.  Where  a 
water-cushion  or  pressure-regulator  alone  is  desired  a  tall  pipe 
of  small  section  is  used;  as  at  Wichita,  Kan.,  where  a  pipe 
2^  feet  in  diameter  and  150  feet  high  was  erected.  Where 
storage  also  is  desired  the  cross-section  area  is  considerably 
increased,  as  at  Houston,  Tex.,  which  erected  a  standpipe 
30  feet  in  diameter  and  150  feet  high,  holding  144  times  as 
much  water  as  the  former.  The  standpipe  may  be  placed 
at  or  near  the  pump,  or  at  some  point  in  the  distribution 
system;  the  highest  ground  in  or  near  the  city  being  ordi- 
narily chosen. 

The  storage-  or  distributing-reservoir  for  a  pumping 
system  differs  in  no  important  particular  from  that  in  a 
gravity  system.  In  order  to  reduce  the  length  of  pumping- 
main,  in  the  indirect  system  the  reservoir  is  placed  as  near 
the  pump  as  sufficiently  high  ground  can  be  found;  but  in 
the  direct-indirect  it  is  preferable  to  locate  pump  and  reser- 
voir on  opposite  sides  of  the  city. 

The  pumping  machinery  must  always  be  at  the  point  of 
supply,  or  at  a  location  which  can  be  reached  by  gravity  from 
such  point.  In  some  instances  it  is  necessary  or  more 
economical  to  place  one  or  more  additional  pumping-plants 
along  the  line  of  the  pumping-main;  as  on  the  Coolgardie 
pumping-main,  which  is  328  miles  long,  the  friction-head  in 


200  WATER-SUPPLY  ENGINEERING. 

which,  if  all  supplied  at  one   point,  would  require  an  almost 
impossible  strength  of  pipe  and  pumps. 

Art.  60.     Intakes  and  Pumping-plants. 

If  water  is  taken  by  the  pumps  from  a  reservoir,  the 
suction  can  pass  from  the  pumps  directly  into  this,  or  water 
can  be  led  from  the  reservoir  to  a  suction-well  placed  under 
or  near  the  pumps.  In  either  case  it  is  desirable  to  place  a 
gate-house  in  the  reservoir,  by  means  of  which  water  can  be 
drawn  from  any  desired  level  of  this. 

If  the  supply  is  from  tube-wells,  these  are  practically 
made  to  serve  as  parts  of  the  suction,  and  are  all  connected 
to  a  pipe  and  through  this  to  the  pump.  This  suction-pipe, 
all  the  connections,  and  the  wells  should  be  absolutely  air- 
tight, since  if  they  are  not,  a  part  of  the  energy  of  the  pump 
will  be  wasted  in  sucking  in  air,  and  the  pump  itself  may  be 
damaged  if  this  enters  the  cylinders.  The  collecting-pipe, 
or  that  to  which  all  the  wells  are  connected,  should  be  at  as 
low  an  elevation  as  the  pumps.  If  wrought-iron  pipe  is  used 
for  this,  particular  pains  should  be  taken  to  obtain  perfect 
screw-tlireads,  that  the  joints  may  be  made  tight.  Cast-iron 
flanged  pipe  is  better  for  this  purpose,  as  tighter  joints  can 
be  made  with  this.  The  size  of  the  pipe  should  be  such  that 
the  velocity  of  flow  through  it  will  not  exceed  one  or  two 
feet  per  second;  and  the  pumps  should  be  so  located  as  to 
make  the  collecting-pipe  as  short  as  possible. 

If  the  supply  is  from  deep,  non-artesian  wells  in  which 
the  water  does  not  rise  higher  than  a  point  40  or  more  feet 
below  the  surface,  a  pump  must  be  placed  in  each  well  to  lift 
the  water  to  the  surface.  If  it  is  to  be  raised  still  higher,  an 
additional  surface  pumping-plant  is  used,  drawing  water  from 
a  suction-well  into  which  the  deep-well  pumps  discharge. 

If  the  supply  is  from  a  river,    care  should   be  taken  to 


PUMPING   SYSTEMS.  20I 

locate  the  intake  at  that  point  which  will  give  the  purest 
supply  at  all  times.  It  should  not  be  placed  in  an  eddy,  or 
in  shallow  or  slack  water  at  one  side  of  the  river,  since  matter 
in  suspension  is  apt  to  collect  here.  It  should  always  be  at 
a  distance  below  the  surface  at  least  twice  as  great  as  the 
diameter  of  the  intake  opening.  It  should  be  at  such  an 
elevation  above  the  bottom  that  no  sand  or  slit  carried  by 
the  bottom  layer  of  water  can  enter  it.  It  should  be  placed 
below  rather  than  above  any  pond  or  slack-water,  unless 
additional  pollution  is  added  to  the  water  there.  It  should 
generally  be  placed  above  the  city,  to  avoid  the  pollution  by 
street-drainage  which  probably  enters  the  river,  even  if  no 
sewers  discharge  into  it.  A  screen  is  generally  placed  over 
the  intake  to  exclude  fish  and  floating  matter;  and  it  should 
be  contained  in  and  protected  by  a  crib  or  masonry  structure. 

If  the  supply  be  from  a  lake  it  is  generally  desirable  to 
place  the  intake  at  the  lower  end  of  the  lake,  in  or  near  the 
channel,  and  to  the  windward  rather  than  the  leeward  of  this. 
It  should  be  as  far  as  practicable  from  the  outlets  of  any 
sewers  or  polluted  streams,  being  if  possible  on  the  opposite 
side  of  the  main  current  from  them. 

The  obtaining  of  these  conditions  often  requires  expensive 
construction.  Heavy  masonry  intake-towers  in  deep  or  swift 
water;  long  and  large  intake  pipes  or  tunnels  connecting 
these  with  the  pumps;  and  deep  pump-pits  protected  from 
heavy  floods  in  the  adjacent  river,  are  all  called  for  in  some 
instances.  On  the  Great  Lakes  intakes  are  placed  four  or 
five  miles  from  shore,  and  in  the  larger  rivers  of  the  Missis- 
sippi basin  are  intake-towers  50  to  140  feet  high,  with  open- 
ings for  taking  water  at  various  levels. 

The  intake-pipes  should  be  well  buried  in  the  bed  of  the 
river  or  lake,  to  prevent  injury  by  currents  or  waves,  by  the 
anchors  of  boats,  or  from  any  other  cause.  They  are  some- 
times made  of  wrought-iron  pipe  imbedded  in  concrete,  but 


202  WA  TEH-SUPPLY  ENGINEERING. 

cast  iron  is  more  substantial  and  durable  if  given  an  unyield- 
ing bed. 

Anchor-  or  slush-ice  collecting  and  freezing  around  intake- 
openings  gives  a  great  deal  of  trouble  in  some  localities. 
This  is  caused  by  needles  of  ice  which  are  prevented  from 
freezing  together  by  the  motion  of  the  water,  and  are  drawn 
into  the  intake  in  this  shape,  generally  freezing  upon  and 
choking  the  screen.  These  needles  are  not  found  in  calm 
water,  where  they  collect  into  sheet  ice  on  the  surface,  and 
seldom  on  the  windward  side  of  a  lake  or  river;  and  are  not 
often  drawn  into  the  intake  when  this  is  well  below  the  sur- 
face, and  of  such  size  that  the  velocity  of  flow  into  it  is  less 
than  one-half  foot  per  second. 

The  motive  powers  adopted  for  raising  water  include  man 
or  animal  power;  water-wheels  and  other  hydraulic  machinery; 
windmills;  gas-,  gasoline-,  oil-  and  hot-air-engines;  steam- 
engines;  electric  motors;  compressed-air-engines;  and  in 
fact  all  kinds  of  motive  power  are  used  for  driving  pumps. 
Compressed  air  and  steam  are  also  used  directly  without  the 
medium  of  pumps,  in  the  air-lift  and  steam-siphon. 

The  pump  and  motor  are  generally  placed  in  the  same 
building,  and  in  most  cases  are  really  parts  of  the  same 
machine.  Animal  power  is  used  but  little  if  at  all  for  any 
but  private  supplies.  Windmills  are  used  on  fe^y•  public 
supplies,  not  being  adapted  to  pumping  large  quantities  of 
water,  and  depending  upon  uncertain  winds  for  power.  Gas-, 
gasoline-,  oil-,  and  hot-air-engines  give  excellent  service  in 
many  small  plants,  but  have  not  so  far  been  used  in  large 
ones;  and  the  same  may  be  said  of  electric  motors,  although 
these  and  compressed-air-engines  will  probably  come  more 
into  use  in  the  near  future.  Hydraulic  machinery  has  been 
used  in  a  number  of  large  plants,  and  gives  excellent  satisfac- 
tion where  the  water-power  is  always  ample.     There  are  not 


PUMPING   SYSTEMS.  203 

many  locations,  however,  in  which  this  is  not  likely  to  fail  in 
times  of  drought,  when  the  demand  for  water  is  greatest.  It 
is  ordinarily  cheaper,  however,  than  most  of  the  other  motive 
powers,  and  the  rate  of  pumping  can  be  increased  at  once  to 
meet  the  demands  of  a  fire  upon  a  direct-pumping  plant.  A 
supplementary  steam-plant  is  in  some  cases  provided  in  con- 
nection with  a  hydraulic  plant,  to  provide  for  pumping  during 
low  water. 

By  far  the  greatest  number  of  pumping-plants  have  steam 
as  a  motive  power;  this  being  adapted  to  the  largest  as  well 
as  the  smallest  engines,  and  being  under  control  at  all  times; 
although  an  immediate  increase  in  delivery  in  case  of  fire 
cannot  be  obtained. 

In  deciding  upon  the  motive  power,  consideration  should 
be  had  of  the  accessibility  of  the  plant  and  its  general  loca- 
tion. An  electric  plant  requires  within  reasonable  distance 
an  electric  power-station  where  power  can  be  generated  more 
cheaply  than  at  the  pumping-station;  hydraulic  machinery, 
a  constantly  abundant  supply  of  water-power.  Steam-plants 
require  coal,  wood,  oil,  or  gas  to  supply  the  heat,  and  the 
means  of  reaching  the  plant  with  these  must  be  considered. 
It  may  be  more  economical  to  place  a  steam-plant  using  coal 
near  a  railroad  and  some  distance  from  the  source  of  water- 
supply,  and  bring  the  water  by  gravity  to  the  pumps,  even 
though  this  require  a  somewhat  greater  lift  and  cost  of  con- 
struction. 

In  the  pump  proper,  as  used  in  city  supplies,  there  is 
little  variation  except  in  detail.  There  are  two  general 
designs;  the  most  efficient  and  one  most  commonly  used 
consists  essentially  of  a  piston  and  valves  so  arranged  that, 
by  a  reciprocating  motion  of  the  piston,  water  is  sucked  in 
through  one  set  of  valves  and  forced  out  through  another;  in 
the  other,  rotating  valves  or  blades  provide  the  suction  and 


204 


JVA  TEE-SUPPLY  ENGINEERING. 


propelling    power.       The     former    are     called     reciprocating 
pumps,  the  latter  rotary  pumps. 

There  are  other  methods  of  raising  water  for  irrigation ; 
as  by  hydraulic  rams,  water-wheels,  and  other  water-driven 
machines;  and  many  devices  for  the  direct  lifting  of  water  in 
buckets  or  barrels,  few  of  which  are  used  in  this  country 
except  in  private  systems. 

METHOD    OF    SUPPLY    TO    CITIES    AND    TOWNS    IN    THE    UNITED 
STATES    IN     1897. 


Method  of  Supply. 


Gravity 

Gravity  and  Pumping  : 

Direct 

To  reservoir 

To  stand-pipe 

Direct  and  to  reservoir 

"      "   stand-pipe 

To  reservoir  and  stand-pipe 

Total 

Pumping  : 

Direct 

To  reservoir 

To  stand-pipe 

To  reservoir  and  stand-pipe 

Direct  and  to  reservoir 

"        "     "  stand-pipe 

"        "      "   reservoir  and  stand-pipe 

Total 

Natural  pressure 

Grand  total 


Districts. 


North-     South-     North      West- 
eastern   eastern    Central      ern. 


490 


62 

38 

II 

I 

3 

4 


41 


119 


194 


15 

13 

5 

I 

I 


Total. 


736 


86 

54 

20 

2 

8 

12 


43 


1S2 


74 
128 

245 
26 

33 

41 

3 


550 


33 
62 

139 

II 

II 

20 

2 


278 


221 

79 

218 

14 

27 
115 

18 


692 


90 
114 

358 

20 

45 

1S5 


41S 

3S3 
960 

71 
116 
361 

33 


822     2,342 


1,159 


339 


714 


1,069 


3,281 


A  pump  must  not  be  placed  at  such  an  elevation  above 
the  water  that  it  cannot  lift  this  to  its  own  level;  which  dis- 
tance cannot  ordinarily  exceed  22  to  25  feet,  although 
theoretically  a  34-foot  lift  is  possible.      This  limitation   may 


PUMPIXG    SYSTEMS.  205 

necessitate  placing  the  pump  far  underground  in  the  case  of 
non-artesian  deep  wells.  Where  a  riv^er  is  subject  to  a  great 
rise  of  level  during  floods,  the  pump  must  be  placed  within 
25  feet  of  the  low-water  level,  although  this  may  be  below 
the  flood-level,  and  in  such  a  case  provision  must  be  made  to 
protect  the  pump  from  flood-water. 

The  table  on  the  preceding  page  shows  the  number  of 
gravity,  direct,  indirect,  and  direct-indirect  pumping  systems 
in  the  United  States  in  1897. 

QUERY. 

17.  In  a  city  of  10,000  inhabitants  is  a  direet-indirect  system, 
with  standpipe  150  high  on  such  level  ground  that  the  bottom  100 
feet  can  furnish  no  supply  for  fire-protection.  If  it  requires  two 
hours  at  night  to  get  the  steam  and  pumps  ready  for  fire-service, 
what  should  be  the  diameter  of  the  standpipe,  the  average  discharge 
of  one  nozzle  being  taken  as  200  gallons  per  minute  ? 


CHAPTER    XI. 

HYDRAULICS. 

Art.  01.     Statics. 

It  is  not  intended  to  give  here  a  demonstration  of  the 
principles  of  hydraulics;  for  these,  reference  may  be  made  to 
any  good  treatise  on  this  subject.  But  it  is  thought  desirable 
to  place  here  for  convenient  use  a  brief  summary  of  the 
general  principles  and  formulas  applicable  to  water-supply 
engineering;  also  tables  of  coefTficients  and  data  for  actual  use. 

(i)  The  pressure  on  any  surface  due  to  water  not  in 
motion  (the  surface  of  this  water,  or  of  some  body  of  water 
with  which  it  is  freely  connected  being  open  to  ordinary 
atmospheric  pressure)  is  equal  to  the  area  of  this  surface, 
times  the  difference  between  the  elevation  of  its  centre  of 
gravity  and  the  elevation  of  the  free  surface  of  water,  times 
the  weight  of  a  unit  volume  of  water.  Pressures  are  usually 
expressed  as  so  many  pounds  per  square  inch,  and  the 
pressure  on  a  square  inch  of  any  surface  is  approximately 
P  =  0.434//"  pounds,  in  which  H  is  the  difference  of  level 
between  the  free  water-surface  and  the  point  in  question, 
expressed  in  feet. 

(2)  When  water  is  motionless  in  a  system  of  pipes, 
throughout  which  it  has  free  communication,  it  will  stand  at 
the  same  level  in  all  connected  branches  wherever  free  to  do 
so;  also  the  same  pressure  will  be  exerted  by  the  water  in 
every  part  of  the  system  which  lies  at  the  same  level :  and 

206 


HYDRAULICS.  20/ 

the  difference  in  pressure  per  square  inch  exerted  at  any  two 
points  will  be  0.434  times  their  difference  of  elevation  in  feet. 
For  example,  if  a  pump  exert  by  its  piston  a  pressure  of  100 
lbs.  per  square  inch  (there  being  no  motion  of  water  in  the 
pipes),  at  a  point  50  feet  higher  the  pressure  would  be 
100  —  (50  X  0.434)  or  78.3  lbs. 

(3)  The  pressure  of  water  is  the  same  in  all  directions  on 
all  points  in  the  same  horizontal  plane. 

(4)  Water  pressure  is  always  normal  to  the  surface  with 
which  it  is  in   contact.      Thus  in 

Fig.  19  the  pressure  is  perpen- 
dicular to  the  back  of  the  dam. 
If  it  were  not,  but  were  for  in- 
stance horizontal,  it  could  be 
resolved  into  two  components,  ^ 
one  normal  and  one  parallel  to  the  Fig.  19. — Pressure  on  Inclined 
surface,  and  the  water  would  rise  urface. 

up  over  the  dam  under  the  influence  of  the  latter. 

(5)  V}y  resolving  a  pressure  into  its  components  the 
pressure  in  any  given  direction  may  be  found;  but  it  follows 
from  (4)  that  there  can  be  no  component  along  the  surface 
under  pressure. 

(6)  From  the  above  it  is  demonstrable  that  the  resultant 
pressure  in  any  given  direction,  exerted  outward  from  within 
or  inward  from  without,  upon  a  given  surface  of  any  pipe, 
vessel,  or  solid  body  containing  or  immersed  in  water,  equals 
the  pressure  in  this  direction  upon  the  projection  of  such 
surface  normal  to  such  direction  and  passing  through  the 
centre  of  gravity  of  such  surface;  this  applying  to  plane  sur- 
faces, and  to  horizontal  pressures  on  all  surfaces;  and  approxi- 
mately to  all  cases  where  the  height  of  a  vertical  projection 
of  said  surface  is  small  relative  to  the  pressure  head  upon  it. 

The  above  statements  are  true  only  when  the  surface  in 
question  is  free  to  normal  atmospheric  pressure,  and  is  strictly 


208  WATER-SUPPLY  ENGINEERING. 

true  only  when  such  pressure  and  that  upon  the  free  water- 
surface  are  the  same.  As  a  matter  of  fact,  the  pressure 
exerted  by  the  water  is  the  amount  given  above  plus  that 
exerted  by  the  atmosphere  upon  the  water-surface  (about 
14.7  lbs.  per  square  inch);  but  is  opposed,  directly  or  in- 
directly, by  the  atmospheric  pressure  exerted  in  the  opposite 
direction  upon  the  surface  considered. 

(7)  The  centre  of  pressure  upon  any  rectangular  surface 
immersed  in  water  and  having  one  end  coincident  with  the 
water-surface  is  in  the  line  which,  being  in  the  rectangle, 
bisects  the  line  of  intersection  of  these  two  surfaces  and  is 
perpendicular  to  it,  being  one  third  the  length  of  this  line 
above  the  lower  end  of  the  rectangle.  The  rectangular  sur- 
face may  be  vertical  or  inclined;  but  only  the  wetted  surface 
is  considered,  any  which  is  above  the  water  not  affecting  the 
problem. 

(8)  The  centre  of  pressure  upon  any  parallelogram,  rect- 
angle, or  square,  having  one  edge  in  or  parallel  to  the  water- 
surface,  may  be  found  graphically  as  follows. 

Let  abed  be  a  parallelogram,  ab  and  dc  being  parallel  to 

the  water-surface  wx.      Let /be  the  middle  of  dc,  and  /the 

^  f,     ^^   middle   of  ab\   continue   the   line 

/"\\rt  //  to  the  water-surface,  as  at  c. 

/  .'.  ;,r ic  -^ 

/  ■' \/\\     \  Draw  ea  and  eb\   also  gk  parallel 

//     7sV-i»(,\\  to  ea,  and^r  parallel  to  //.     Draw 

1 — ^H ^r  ^li  parallel  to  ab  and  ed,  and  half- 

a      k      I    r         0  ^  ' 

Fig.  20.— Centre   of   Pressure  way  between  them.      Let  ;/  be  the 
UPON  A  Parallelogram.         centre   of  ho,  and   mr  equal   ^rg. 
Connect  in  and  n;   and  where  mn  cuts  el,  or  s,  is  the  centre 
of  pressure. 

(9)  The  general  rule  for  the  centre  of  pressure  of  an 
immersed  plane  surface  is:  The  distance  from  the  water-sur- 
face to  the  centre  of  pressure,  measured  in  the  plane  of  the 
immersed  surface  and  normal  to  the  line  of  its  intersection 


HYDRAULICS.  2O9 

with  the  water-surface,  equals  the  quotient  of  the  moment  of 
inertia  of  such  surface  by  the  static  moment,  both  with  refer- 
ence to  that  hne,  as  an  axis,  which  is  formed  by  the  inter- 
section of  the  plane  with  the  water-surface. 

(10)  The  pressure  upon  the  bottom  of  an  immersed  body 
is  greater  than  that  upon  the  top;  and  if  the  sum  of  the 
vertical  downward  components  of  the  pressure  upon  all  sides 
of  such  a  body  plus  its  weight  be  greater  than  the  sum  of  the 
vertical  upward  components,  the  body  will  sink;  if  such  sum 
be  less,  the  body  will  rise  and  float  upon  the  surface.  A 
floating  body  will  sink  in  the  water  to  such  a  depth  that  the 
weight  of  water  displaced  by  it  just  equals  its  own  weight. 

The  force  necessary  to  support  an  immersed  body,  or  its 
downward  pressure,  will  be  as  much  less  in  water  than  in  air 
as  is  the  difference  between  the  downward  and  upward 
vertical  components  of  the  pressure  upon  it;  which  is  the 
weight  of  the  volume  of  water  displaced.  If  water  finds  its 
way  under  any  part  of  a  stone  dam,  the  effective  weight  of 
such  dam  is  reduced  by  62.5  lbs.  per  square  foot  of  horizon- 
tal wetted  joint,  times  the  depth  of  such  joint  beneath  the 
water-surface. 

Art.  62.     Flow  in  Open  Conduits. 

The  flow  in  a  conduit  is  due  to  gravity  alone,  as  brought 
into  action  by  a  fall  in  the  water-surface.  The  velocity  is 
affected  by  the  size  and  form  of  cross-section  of  the  conduit, 
and  the  nature  of  its  surface.  The  velocity  at  any  particular 
point  may,  however,  be  increased  or  decreased  by  conditions 
above  or  below  such  point.  The  ordinary  formulas  for  flow 
consider  only  cases  of  uniform  velocity  and  cross-section  for 
some  distance  above  and  below  as  well  as  throughout  the 
section  under  discussion. 

Flow  has  been  found  to  vary  to  a  certain  extent  with 
the    relation    between    the    cross-section    of    the   stream    and 


2IO 


WATER-SUPPLY  ENGINEERING. 


the    wetted    part    of    the   perimeter;    and    this    relation,    or 

cross-section  ,  ,  .  ,  ><  i     j       i- 

: ,    has    been    given    the    name        hydraunc 

wetted    perimeter 

radius,"  and  is  customarily  represented  by  r.  For  a  semi- 
circular or  circular  cross-section  of  f^ow  r  is  one  fourth  the 
diameter. 

(i  i)  The  velocity  given  by  formulas  is  the  mean  velocity. 
That  at  the  surface  and  along  the  wetted  perimeter  is  less 
than  this  (except  when  wind  blowing  down-stream  increases 
the  surface  velocity).  The  mean  velocity  in  rivers  is  gen- 
erally about  98^  of  the  mid-depth  velocity  and  from  70  to 
85  per  cent  of  the  maximum  surface  velocity. 

(12)  The  Chezy  formula,  F=  c\^rsy  is  generally  used  as 
the  basis  of  velocity  formulas,  where  F  is  the  mean  velocity 
in  second-feet,  c  is  a  constant,  r  is  the  hydraulic  radius,  and 
s  is  the  tangent  of  the  slope  or  rate  of  fall  of  the  surface  (and 
also  of  the  conduit). 

Values  of  c  adapted  to  different  conditions  have  been 
ascertained  by  experiment.  For  metal,  wood,  concrete,  or 
smooth  masonry  conduits  of  circular  section  Hamilton  Smith 
gives  the  following  values  for  c\ 

Table  No.  4G. 

COEFFICIENT    C    FOR    SMOOTH    CIRCULAR    OR    SEMI-CIRCULAR 
CONDUITS. 


Veloc- 

Diameters.      D  =  ^r. 

ity  V. 

.05 

.10 

I 

1-5 

- 

2-5 

3 

3-5 

4 

5 

6 

7 

8 

2 
3 
4 
5 
6 
7 
8 

9 
10 
II 
12 
13 
14 
•5 

20(?) 

"17.9,' 
82.4 
85.6 
87.6 
89.1 
90.0 
90.6 
90.7 
90.8 
90.9 
91 .0 
91.0 
91.0 
91.0 

80 
88 
93 
97 
99 

lOI 

102 
103 
104 
104 
104 
104 
105 
105 
105 

0 

9 

7 
0 

3 
0 

4 
3 
0 
5 
7 
8 
0 
0 
0 

96 
104 
loS 
112 
114 
116 
n8 
"9 
120 
121 
122 
122 
122 
123 
123 
123 

I 
0 
7 
0 
4 
3 

3 
4 
4 
0 
5 
9 
2 
6 
9 

I02.8 

110.9 
115. 6 
118. y 
121. 3 
123.2 
125.0 
126.4 
127.7 
128.8 
129.7 
130.4 
131 .0 
'3'-5 
131. 8 
132.9 

108.8 
116. 2 
120.8 
124.0 
126.5 
128.6 
130.4 
132.0 
'33-3 
'34-5 
135.6 
136.4 
137. 1 
137.'^ 
138.0 

112 
120 
124 
128 
130 
132 
134 
136 
137 
139 
140 
141 
141 
142 
142 

7 
3 
8 
I 

6 
6 
6 
3 
7 

2 

1 
9 
5 
9 

116 
123 
128 
131 
134 
136 
138 
140 
141 
142 
144 
145 
,46 
,46 
M7 

7 
8 
3 

5 
I 
3 

2 

6 

9 
2 
2 

I 
7 

2 

120.2 
127.0 
131.4 
134.6 

137. 1 
139.4 
141.5 

M3-3 
145.0 
146.4 
147-7 
148.8 
149.8 
150.5 
151. 1 

123.0 
129.9 
134.2 
137-4 
140.0 
142.3 
144.5 
146.3 
148. 1 
149.7 
151. 0 
152.2 
153-2 
154-0 
'54-6 

127.8 
134-3 
138.0 
141. 9 
144.7 
146.9 
149.0 
151. 0 
152.8 
154.6 

131. 8 
138.0 
142.3 
145-5 
148.1 

150-5 
152.7 

154-9 
156-7 

134.8 
141 .0 
145.4 
148.6 
151. 2 
153-5 

137-5 
M3-3 
147.6 
151.0 
153-6 

HYDRA  Ur.ICS. 


211 


Smith  also  gives  the  following  values  for  rectangular  con- 
duits, b  =  breadth  of  conduit,  d  =  depth  of  water  flowing. 

Table  No.  47. 
coefficient  c  for  rectangular  and  trapezoidal  conduits. 


Rectangular  Conduits. 

For  depth  of 

1.64  ft.  sides 

inclined  45°, 

and  then 

vertical. 

Pure  Cement. 

5  =    .0049 

6  =  5.94 

Brick  (not  very 
smooth). 

S~    .0049 
6  =  6.27 

Unplaned 
Plank. 

5  =     .00824 
-5  =  6.53 

Unplaned 
Plank. 

S-     .0015 

i  =  6. SI 

Unplaned 
Plank. 

S  =     .006 
i  =  1-575 

Unplaned 
Plank. 

S  =  .0015 
Bottom  1^=3.28 

d 

c 

d 

c 

d 

c 

d 

c 

d 

c 

d 

c 

18 
28 
38 
43 
50 
56 
63 
69 
76 
80 
86 
91 

116. 5 
125. 1 
126.9 

132.4 
132.4 

135. 1 
135-5 
136.2 
137.2 
137.2 
137.8 
138.2 

20 
31 
41 

49 

57 
65 
71 
77 
85 
90 

97 
04 

89 
98 
98 

103 

105 

103 
106 
loy 
107 
no 
109 
108 

7 
3 

8 

7 

I 
7 
3 
0 

4 
8 

7 

7 

15 
25 
32 
38 
45 
50 
54 
60 

65 
69 
74 
78 

IOI.4 
IOI.4 
107. 1 
109.8 

109.7 

113.1 
115. 8 
115.2 

115. 8 

116. 9 
117. 1 
119. 0 

•30 

.46 

.72 

.92 

I  .  10 

1.27 

1.44 

88 
96 
104 
no 
115 
119 
120 

3 
3 
2 

4 
r 
I 
4 

34 
44 
50 

53 
62 
70 
79 
87 
95 

94 
97 
98 

97 
102 
104 
105 
105 
107 

5 
3 
3 
I 

3 
6 

3 

7 
9 

•92 
I.  19 
1.40 

1-55 
1 .69 
1.82 

1-93 

2.03 
2.13 
2.22 
2.30 
2.37 

103 
no 

"3 
116 

"7 
117 
118 
118 
119 
119 
119 
120 

I 

4 
0 
2 
6 

3 
0 

4 
0 

5 
4 
9 

For  earth  channels  Kutter's  formula  probably  gives  the 
most  accurate  values  for  c,  as  also  indeed  for  those  referred 
to  by  the  above  tables.  This  formula,  with  feet  and  seconds 
as  the  units  of  measurement,  is  as  follows: 


(13) 


c  = 


1. 81                       0.0028 
___|_  41.65 -^ — 

~(      ^      ,   0.0028/ 
n[4i.6s  H ^j 


1  + 


Vi 


in  which  «  is  a  coefficient  of  roughness  of  the  wetted  surface 
of  the  conduit,  and  is  given  values  as  follows: 


212 


WATER-SUPPLY  EN'GINEERING. 


(14)  For  channels  of  well-planed  timber 009 

"  "  "  neat     cement,     glazed     sewer-pipe,     or    very 

smooth  iron  pipe,  and  butt-joint  w.  i.  pipe.   .010 

"1:3  cement  mortar  or  smooth  iron  pipe on 

"   unplaned  timber  and  ordinary  cast  iron 012 

"   smooth  brickwork 013 

"  ordinary  brickwork  or  smooth  masonry 015 

"  lap-joint  wrought-iron  pipe 012  to  .016 

"  "  "  rubble  masonry =, .    017 

"  "  "  firm  gravel 020 

"  "  "  rivers  free  from  stones  and  weeds 025 

"    canals  and  rivers  with  some  stones  and  weeds C30 

"  "  "  "       in  bad  order 035 

If  the  velocity  V  be  calculated  for  a  given  hydraulic 
radius  and  grade  with  a  value  for  ;/  of  .011,  an  approximafe 
value  of  V  for  other  values  of  n  can  be  obtained  directly  by- 
multiplying  the  first  value  of  V  by 

1.25  when  the  second  n  is  .009 


1. 10     ' 

''    .010 

1. 00     ' 

'        "     .oil 

.90    ' 

'            "       .012 

.80    ' 

-       .013 

.70   ' 

"       .015 

.60    ' 

-      .017 

Considerable  care  must  be  used  in  selecting  the  proper 
value  of  n\  and  an  actual  measurement  of  the  flow  is  always 
to  be  preferred  to  the  best  formula  used  with  the  most  expert 
judgment.  Pipes  of  metal  or  wood  being  of  a  uniform  known 
material  and  cross-section,  flow  through  them  is  capable  of 
more  accurate  determination  than  that  through  channels  of 
earth  or  ordinary  masonry.  These  will  be  taken  up  more  at 
length  in  Art.  63. 

(15)  In  passing  around  curves  the  greatest  velocity  will 
be  along  the  outer  side,  and  that  along  the  inner  side  may 
be  zero,  or  even  a  reversed  current  or  eddy.  There  will 
generally  be  cross-currents  here,  also,  from  the  inner  to  the 


HYDRAULICS.  213 

outer  side  on  top  and  in  the  reverse  direction  on  the  bottom; 
and  the  result  of  these  will  be  erosion  of  the  outer  bank  of  a 
canal  or  river  and  deposits  on  the  inner.  Velocity  at  curves 
should  therefore  be  small,  or  the  bank  should  be  paved  or 
otherwise  protected  from  erosion.  The  cross-currents  also 
cause  friction  between  the  particles  of  water,  which  friction 
must  result  in  a  loss  of  head. 

(16)  The  energy  stored  in  a  moving  body  of  water  varies 

directly    as   its   mass   and    as   the   square    of   its  velocity,    or 

W 
E  =^  — F\    in    which    IV  is   the  weight   in   pounds  of  water 

passing  a  given  point  in  one  second,  g  is  32. 16  feet,  and  V  is 
the  velocity  of  flow  in  feet  per  second.  Since  W  varies  as 
V,  E  varies  as  f . 

W 

(17)  The  impulse  of  a  moving  body  of  water  equals  —  V, 

and  hence  varies  as  the  square  of  the  velocity.  Any  curve 
in  the  connning  channel  of  a  body  of  flowing  water  receives 
an  impulsive  pressure  in  the  direction  of  original  flow  and 
must  be  strengthened  to  resist  such  pressure. 

(18)  The  amount  of  pressure  received  is 


(-F](i-cos^), 


in  which  6  is  the  angle  between  the  original  direction  of  flow 
and  that  after  deflection.  If  6  is  greater  than  90°,  cos  6 
becomes  minus,  and  the  second  factor  of  the  equation 
becomes  greater  than  i. 

(19)  A  contraction  or  expansion  of  the  area  of  cross- 
section  by  an  ofTset  causes  a  loss  of  head  due  to  the  eddies 
created;  which  can  be  avoided  by  sloping  or  rounding  the 
offset  so  as  to  provide  a  gradual  increase  or  decrease  of  sec- 
tional area. 


214  WATER-SUPPLY   ENGINEERING. 

(20)  The  theoretic  value  of  the  head  lost  in  enlargement 
by  a  right-angle  offset  is 

in  which  V  is  the  velocity  of  flow  before,  and  P",  that  after 
enlargement. 

(21)  The  theoretic  value  of  the  head  lost  in  contraction 
by  a  right-angle  offset  is 

2^ 
in  which  C  varies   between  o  and  \,  according  to  the  ratio 
between  the  two  areas  of  cross-section. 

This  loss  may  be  caused  by  projections  in  the  sides  or  in 
the  bottom  of  a  canal  or  flume,  and  may  be  utilized  to  reduce 
velocity  of  flow  without  decreasing  the  fall.  But  the  loss  is 
due  to  eddies,  and  provision  must  be  made  for  resisting 
erosion  by  these. 

(22)  If  a  river,  canal,  or  other  body  of  flowing  water  be 
obstructed  by  a  weir,  the  surface  elevation  is  raised  at  such 
point,  and  for  a  considerable  distance  back  from  such  point, 
"  back-water"  being  thus  formed.  A  high  overfall  dam,  or 
weir,  in  a  river  may  cause  considerable  land  to  be  flooded, 
and  it  is  desirable  to  know  to  what  extent  this  flooding  will 
reach  during  both  high  water  and  the  ordinary  flow.  This 
can  be  determined  approximately  from  the  formula 


I 


^  +  -(7-ll<i)-Kl)' 


in  which  d^  is  the  depth  of  water  just  back  of  the  weir,  d^  its 
depth  at  a  distance  L  above  the  weir,  i  is  the  slope  of  the 
river-bed  and  original  water-surface,  D  is  the  original  depth 
of  water,  c  is  the  coefficient  in  the  formula    F=  cVrSy  and 

<P\-f\   and  ^\-f\   are  abbreviations  for  logarithmic  functions 


HYDRAULICS. 


215 


of  these  quantities,  the  values  of  which  functions  are  obtain- 
able from  Table  No,  48  (from  Merriman's  "  Hydraulics," 
which  see  for  fuller  discussion). 

Table  No.  48. 

VALUE    OF    THE    BACK-WATER    FUNCTION    4'\~J^\' 


D 
d 

*G4)   ' 

.?      ^ 

Ai) 

J      < 

Ai) 

D 

i 

*{^) 

I 

cc 

948 

S6S5 

815 

4454 

52 

•1435 

0.999 

2.1834  i 

946 

•8539 

810 

4367  I 

51 

.1376 

998 

1-9532  1 

•944 

8418 

805 

4281 

50 

-1318 

997 

I. 8172 

942 

S301 

800 

.4198  ; 

•49 

.  1262 

996 

I. 7213 

940 

8188 

795 

4117 

48 

.1207 

995 

1.6469  ' 

93S 

8079 

790 

4039 

•47 

-1154 

994 

I. 5861 

93f' 

•7973 

785 

3962 

.46 

.1102 

993 

1-5348 

934 

7871 

780 

.3886 

■45 

.1052 

992 

1.4902 

932 

7772 

775 

3813 

44 

.  1003 

991 

1-4510  1 

930 

7675 

770 

3741  ! 

43 

•0995 

990 

1-4159 

92S 

75S1 

•765 

3671 

42 

.0909 

989 

1-3841 

926 

7490 

760 

.3603 

41 

.0865 

988 

I-355I 

924 

7401 

755 

3526 

40 

.0S21 

9S7 

1.3248  ' 

922 

7315 

750 

3470 

39 

-0779 

986 

1-3037  \ 

920 

7231  I 

745 

3406 

38 

.0738 

9S5 

1.2S07 

918 

7149 

740 

3343 

37 

.0699 

984 

1.2592 

916 

7069 

735 

3282 

36 

.0666 

983 

1.2390 

914 

6990 

730 

3221 

35 

.0623 

982 

1. 2199 

912 

6914 

725 

3162 

34 

.0587 

981 

I. 2019  i 

910 

6839 

720 

3104 

33 

•  0553 

980 

I. 1848 

908 

6766 

715 

3047 

32 

.0519 

979 

1,1686 

906 

6695 

710 

2991  ) 

31 

.04S6 

978 

I-I53I 

904 

6625 

705 

2937  1 

30 

•  0455 

977 

1-1383 

902 

6556 

70 

2883  i 

29 

-0425 

976 

1.1241 

900 

6489 

69 

277S 

28 

•0395 

975 

1.1105 

895 

6327 

68 

2677 

27 

.0367 

974 

1.0974 

890 

6173 

67 

2580  , 

26 

.0340 

973 

1.0848 

885 

6025 

66 

24S6 

25 

•0314 

972 

1.0727 

880 

5S84 

65 

2395  1 

24 

.0290 

971 

I. 0610 

S75 

5749 

64 

2306 

23 

.0266 

970 

1.0497 

870 

5619 

63 

2221 

22 

.0243 

968 

1.0282 

865 

5494 

62 

2138 

21 

.0221 

966 

1.0080  1 

860 

5374 

61 

2058 

20 

.02or 

964 

0.9890 

S55 

5258 

60 

1980 

18 

.0162 

962 

0.9700 

S50 

5146 

59 

1905   ! 

16 

.0128 

960 

•9539 

845 

5037 

58 

1832  \ 

14 

.0098 

958 

-9376 

840 

4932 

57 

I  761 

12 

.0072 

956 

.9221 

835 

4831 

56 

1692 

10 

.0050 

954 

•9073 

830 

4733 

55 

1625   1 

06 

.0018 

952 

.8931 

825 

4637 

54 

1560   I 

•950 

•8795 

820 

4544 

53 

1497 

2l6  IVATER-SUPPLY  ENGINEERIXG. 

(23)  The  weight  of  individual  particles  of  foreign  matter 
which  a  given  stream  can  carry  varies  (theoretically)  as  the 
sixth  power  of  the  velocity.  The  total  amount  which  a 
stream  can  carry  is  uncertain,  but  has  been  found  to  be  as 
high  as  \oic  of  the  weight  of  water.  The  amount  carried,  as 
well  as  the  size  transportable,  varies  as  some  power  of  the 
velocity,  and  hence  a  retardation  of  the  velocity  tends  to 
cause  deposits.  The  following  table,  from  Dubuat,  is 
deduced  from  experiments  in  wooden  troughs.  Channels 
formed  of  such  materials  firmly  compacted  will  not  ordinarily 
be  eroded  by  several  times  these  velocities. 

Table  No.  49. 
power  of  currents  to  transport  loose  materials. 

Material.  Mean  Velocity  of  Current,  Ft.  per  Sec, 

Fine  clay 0.4 

Fine  sand 0.5 

Small  gravel 0.8 

Large  gravel 1.6 

Water-worn  gravel,  about  one  inch  diameter  3.5 

Angular  stones,  i^  to  2  inches  diameter 4.5 

Art.  63.     Flow  in  Pressure  Conduits. 

The  Ch^zy  formula  (12)  is  adopted  as  the  basis  of  velocity 
formulas  for  pressure  conduits  also,  c  being  determined  for 
these  by  experiment.  More  experiments  have  been  made 
upon  cast-iron  pipe  than  upon  any  other;  but  in  recent  years 
the  increasing  use  of  wood-stave  and  riveted  iron  and  steel 
pipes  has  led  to  experiments  with  these  also. 

The  values  of  c  for  different  sizes  of  pipe  and  different 
velocities  of  flow  in  new  cast-iron  pipes,  adapted  from 
Smith's"  Hydraulics"  and  obtained  by  him  from  the  results 
of  a  large  number  of  experiments,  are  given  in  Plate  XII. 

(24)  Tjuberculated  pipe  will  give  a  much  smaller  discharge 
than  new,  partly  because  of  decreased  diameter  and  partly 
because  of  the  greater  roughness  of  surface.     A  4-inch  pipe 


HYDRA  ULICS. 


217 


VELOCITY  IN  FEET  PER. SEC. 
2                     4                      6                     8                    10 

-^      ______   — _^ __ 

-^"'"'^^^^      :""             ='■"    - 

r-^            ^-                             ^^                                       --^^ 

^       -»^             ^^                        ^''                   -                   -'^'^                                                         1 

'^^^     ,"=:               ^-^                         ^''            --                     -"' 

-■^^^     ^^           ^"                     ^-''            -                       ^-^ 

,^>.^     4/            ^^                      ^-            ^                      ^-' 

41                             ^?2%,^X^     ^/'^               ,^-            .-                ."' 

d^^     ^-^        jt'^               ,-"'        _-               ^-"                  ^^-' 

^S^    ^'^       ^<            ^-'       ^            ,^-              ,^'=' 

/<3^    2:       ^/       ^    ^/'^    ,-             ,^='               ^-^^ 

%       "^    i^          <.^^    -•              -•"               ---                        -'-' 

V        ^        ^              ^-'l'            ^-^              ^'-'                    --''' 

^^    ^      ^--    ^-^      w-^      ^-^-^           -"                -'"                     1 

-,Z    4    V         ^      $    -^-^            ^-=''              ^-                             ^' 

Z    y      Z        2^--        ^        ^^^^             ^-'                     ,^''' 

V    V      2        y    *!        ^--^     .    -^           ,--                     ^-''-' 

7^^^  z     ,7   -     ,/      zte^        ^^               ^^ 

-     ^  ^  ^     7-          'f     ^-^^      ^^"              -=^ 

v!    Z!^-^    ^^-^     ^'^       ^^"^       ^V''^              -"^^                                -■'^'" 

12  1  -7  ■    /"     ^^     ^^^^   ^  ^^^^                    ^^--'- 

Vv     z  •   .^     ^/     ^^^        1-^               =,-^ 

2  t   Ji   L   z.      J'     J^          J^^                   ^'^                       ^      I 

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^  V-/  ^    ^      ^-^          -S'         ^--'"  ^--''' 

i    7^y^    y"^    z:"^      ^'^           ^^           -- '      --"' 

I^  6   ^v    ^      ^^          ^^            -•'     --"          --  '               --  - 

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71^        Z                /           '         ^           '            '  • '^                    ■--"'' ^      1 

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7   r    /      ^   ^      -^31      ^^      ^■- 

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-    t^    4    -r    y       'i    ^^^     -       V  -'             -,^-'                                -    -••1 

tt    '    Z  /  ■■      ■     ^^   jS      ,-■                 -^                          ■■-■  -            ' 

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71.     •^'^"_      7    ^-^    it      ^^■-                --■        ^--  --                    

Ati  '  z^_-   7  ^            --         .- ..-■-    __...-•■-- 

ift  j.^~  7  ,-   ,■      . '*     ^^    .-^       .-^            ^^- 

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^^"^  '^^    '  Ji     ■    ^'jz-'^-"            ^-  ■■   " 

^/^^     ^    ^    .    ^    ^^                .*^ 

jzz^    ■        ■    -^         2^                                  __  _ 

7  ?:  :i  ^   ■      -  .^        .-•                           .- ""-" 

'  '  1  ■      '      .                          ■     y'                       '                                                         -  '  '  '     ' 

Zp'^   ^^-  ^""/"      _-•               ^   ,•■''-■"' 

^•^-  ■    "^ -."^^       ^                         st- 

SZ         "•-    ■"^                          _--^                   ^i'       ^ 

"^^    ^^    77           -                 ^.  -                   ^^^Ji?^ 

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7"'-        •   '        ."^                               ^-^             .          .  t     .  -  '  -  ' 

■'  ^Z.'^  -'t     '        ^'        ^^            %■  '"" 

"^     '^-^X                      -^"^           -•     ^' 

1                ■'        Z.            ^                              3fc  -  ■ 

L^      ^      ^      -                   ^--^^ 

"    ^      Z 

7^         /:     - 

l'^    ^     y 

^^  J   z 

Z^                                                                  ___ 

2                       4                       6                       8                     10 

150 


140 


130 


120 


(- 

2 

UJ 

1105 

Ul 

o 
o 


100 


90 


80 


Plate  XII. — Coefficient  c 

(From  Coffin's  "  Graphical  Solu 


FOR  New  Cast-iron  Pipes. 

tion  of  Hydraulic  Problems.") 


2l8  WATER-SUPPLY  ENGINEERING. 

38  years  old  has  been  found  to  discharge  but  one  eighth  the 
amount  indicated  by  the  above  diagram  for  a  new  4-inch 
pipe;  and  the  discharge  of  a  48-inch  pipe  was  decreased  25 
to  30  per  cent  by  tuberculation;  the  difference  in  percentage 
of  decrease  in  these  two  pipes  being  largely  due  to  the  fact 
that  tubercles  seldom  attain  a  height  greater  than  i  or  i-^ 
inch,  regardless  of  the  size  of  pipe,  and  the  available  cross- 
section  was  hence  reduced  by  a  much  larger  proportion  in  the 
4-inch  than  in  the  48-inch  pipe. 

The  necessity  of  giving  values  for  c  corresponding  to  so 
many  sizes  of  pipe  and  velocities  is  avoided  by  giving  values 
for  ;/  in  Kutter's  formula;  or  for  /  (called  the  "  friction 
factor  ")  in  the  theoretic  formula 


(25)  V  =  \l^^' 


in  which  Ji  is  the  head  lost  in  overcoming  friction  in  a  pipe 
of  a  length  /and  diameter^.  The  table  on  page  219  gives 
values  for/ in  this  formula,  or  in  its  modified  form, 

,       flV 

for  clean  iron  pipe,  laid  with  close  joints. 

For  very  smooth  pipes,  similar  to  lead  or  brass,  3^  inches 
or  less  in  diameter,  and  for  these  only,  the  following  formula 
is  proposed  by  E.  B.  Weston,  being  deduced  by  him  from  a 
comparative  study  of  a  large  number  of  experiments: 

0.0^  I  ■;  —  o.o6d 

/=°-°'^«  +  — ^f — ,       , 

from  which  formula  the  table  on  page  220  was  prepared. 
(See  Trans.  Am.  Soc.  C.  E.,  vol.  XXII.  page  55.) 


HYDRAULICS.  219 

Table  No.  50. 
friction    factors  for   pipes. 
(Compiled  by  Merriman  from  Smith,  Fanning,  and  others.) 


Diam- 

Velocity 

in  Feet  per 

Second. 

eter 

in 

Feet. 

X 

2 

3 

4 

6 

10 

'5 

0.05 

0.047 

0.041 

0.037 

•034 

.031 

.029 

.028 

O.I 

.038 

.032 

.030 

.028 

.026 

.024 

.023 

0.25 

.032 

.028 

.026 

.025 

.024 

.022 

.021 

0.5 

.028 

.026 

.025 

.023 

.022 

.020 

.019 

0.75 

.026 

.025 

.024 

.022 

.021 

.019 

.018 

I 

.025 

.024 

.023 

.021 

.020 

.018 

.017 

1.25 

.024 

.023 

.022 

.020 

.019 

.017 

.016 

1-5 

.023 

.022 

.021 

.019 

.018 

.016 

.015 

1.75 

.022 

.021 

.020 

.018 

.017 

.015 

.014 

2 

.021 

.020 

.019 

.017 

.016 

.014 

.013 

2.5 

.020 

.OIQ 

.018 

.016 

.015 

.013 

.012 

3 

.019 

.018 

.017 

.015 

.014 

.013 

.012 

3-5 

.oiS 

.017 

.016 

.014 

.013 

.012 

4 

.017 

.016 

.015 

.013 

.012 

.Oil 

5 

.016 

.015 

.014 

.013 

.012 

6 

.015 

.014 

.013 

.012 

.Oil 

By  (25)    \ 


-\l     fl' 


But   for   a  full 


pipe 


d 

4' 


or 


d^^\r\    and   h/l=^s',    consequently   this   equation    becomes 


V 


-si 


f 


rs.      Comparing    this    with    the    Chezy    formula, 
6.04 


V  =^  c  \  rs,  we  find  c  ^  \  /  — 


/?>g        16 


'/ 


;  and  by  this  equation 


Plate  XII  can  be  compared  with  Tables  Nos.  50  and  51. 

(28)  The  value  of  n  in  Kutter's  formula  for  new  cast-iron 
pipe  is  approximately  .0115,  but  varies  with  the  velocity, 
especially  for  pipes  under  18  or  20  inches  diameter;  although 
this  may  be  due  to  the  greater  effect  in  small  pipes  than  in 
large  of  variation  in  the  rugosity  of  the  surface,  due  to  differ- 
ences in  the  application  of  the  tar-coating  or  to  tuberculation. 


220 


WA  TER-SUPPL  Y  ENGINEERING. 

Table  No.  51. 

friction  factors  for  smooth  pipes. 


Ve- 

Diameters of  Pipes 

n  Feet  and  Inch 

es. 

locity 

in  Feet 

per 

3.0417' 

0.0521' 

0.0625' 

0.0833' 

0.1042' 

0. 1250 

0. 1667 

0.2083 

0.2500 

0.2917 

Second. 

^" 

%" 

VaI' 

i" 
.0964 

i!4" 
.0924 

iJ^" 

2" 

2^" 

3" 

3^" 

O.  lO 

0.1043 

.1023 

.1004 

.0885 

.0806 

.0727 

.0648 

.0569 

0.50 

0.0536 

.0527 

.0518 

.0501 

.0483 

.0465 

.0430 

•0395 

•0359 

.0324 

1. 00 

.0416 

.0410 

.0404 

.0391 

•0379 

.0366 

.0341 

.0316 

.0291 

,  .0266 

1.20 

.0391 

.0385 

.0381 

.0367 

.0356 

•0343 

.0319 

.0296 

.0274 

.0250 

1.40 

•0371 

.0365 

.0363 

•0347 

■0338 

.0324 

.0304 

•0283 

.0262 

.0239 

1.60 

.0356 

.0348 

.0350 

-0332 

.0323 

.0312 

.0292 

.0272 

.0252 

.0232 

1.80 

.0342 

.0336 

.0340 

.0321 

.0313 

.0302 

.0284 

.0265 

.0246 

.0226 

2.00 

.0331 

.0327 

.0322 

•  0313 

•0305 

.0296 

.0278 

.0260 

.0243 

.0225 

2.50 

.0310 

.0306 

.0300 

.0294 

.0286 

.027S 

.0262 

.0246 

.0230 

.0.14 

3- 00 

.0293 

.0290 

.0286 

.0279 

.0272 

.0265 

.0250 

.0236 

.0221 

.0207 

3  50 

.0281 

.0278 

.0274 

.0268 

.0260 

•0254 

.0242 

.0228 

.0214 

.0201 

4.00 

.0271 

.0268 

.0265 

.0259 

.0252 

.0246 

•0234 

.0221 

.0209 

.0196 

4- 50 

.0263 

.0260 

.0256 

.0251 

.0244 

.0238 

.0227 

.0216 

.0204 

.0192 

5.00 

.0256 

.0253 

.0250 

.0244 

.0238 

■0233 

.0222 

.0211 

.0200 

.0189 

5.50 

.0250 

.0246 

.0244 

.0238 

.0234 

.0228 

.0218 

.0207 

.0190 

.0186 

6.00 

.0244 

.0242 

.0239 

.0234 

.0229 

.0224 

.0214 

.0204 

.0193 

.OIS3 

6.50 

.0240 

.0236 

•  0235 

.0230 

.0225 

.0220 

.0210 

.0200 

.0190 

.0181 

7.00 

.0236 

•  0233 

.0230 

.0226 

.0222 

.0217 

.0207 

.0198 

.OI8S 

.0179 

7.50 

.0232 

.0229 

.0227 

.0222 

.0218 

.0214 

.0204 

.0195 

.0186 

.0177 

8.00 

.0229 

.0226 

.0224 

.0220 

.0215 

.0211 

.0202 

.0193 

.0184 

•0175 

.8.50 

.0225 

.0223 

.0221 

.0216 

.0212 

.0208 

.G200 

.0191 

.0182 

.0174 

9.00 

.0222 

.0220 

.0218 

.0214 

.0210 

.0206 

.0198 

.0189 

.0181 

.0173 

9-50 

.0220 

.0218 

.0216 

.0212 

.0208 

.0204 

.0196 

.0188 

.0180 

.0172 

10 

.0218 

.0216 

.0214 

.0210 

.0206 

.0202 

.0194 

.0186 

.0178 

.0x70 

II 

.0214 

.0212 

.0210 

.0206 

.0202 

.0198 

.0191 

.0184 

.0176 

.0168 

12 

.0210 

.0208 

.0206 

.0203 

.0199 

.0195 

.0188 

.0181 

.0174 

.0166 

13 

.0206 

.0205 

.0203 

.0199 

.0196 

.0193 

.0186 

.0179 

.0172 

.0165 

14 

.0204 

.0202 

.0200 

.0197 

.0194 

.0190 

.0184 

.0177 

.0170 

.0164 

15 

.0201 

.0200 

.0198 

.0195 

.0191 

.0188 

.0182 

•0175 

.OI6S 

.0162 

16 

.0199 

.0197 

.0195 

.0192 

.0189 

.0186 

.0180 

.0174 

.0167 

.0161 

17 

.0196 

.0195 

.0194 

.0190 

.0187 

.0184 

.0178 

.0172 

.0166 

.0160 

18 

.0194 

•0193 

.0192 

.0188 

.0186 

•0183 

.0177 

.0171 

.0165 

.0159 

19 

.0193 

.0191 

.0190 

.0187 

.0184 

.0181 

•0175 

.0169 

.0164 

.015S 

20 

.0191 

.0189 

.0188 

•  01S5 

.0182 

.0180 

.0174 

.0168 

•0163 

•0157 

25 

.0184 

•0183 

.0182 

•  0179 

.0177 

.0174 

.0169 

.0164 

.0159 

•0154 

30 

.0179 

.0178 

.0177 

.0174 

.0172 

•  0170 

.0165 

.0161 

.0156 

.0152 

35 

•0175 

.0174 

•0173 

.0171 

.0169 

.0167 

.0162 

•0158 

.0154 

.0150 

40 

.0172 

.0171 

.0170 

.0168 

.0166 

.0164 

.0160 

•0156 

.0152 

.0148 

50 

.0167 

.0166 

.0165 

.0163 

.0162 

.0160 

.0156 

.0153 

.0149 

.0146 

(29)  For  wood-stave  pipe,  ;/  and  the  friction-factor  have 
generally  been  found  less  than  for  cast-iron  pipe.  For 
30-inch  pipe  on  the  Denver  water-works  n  was  found  to  be 
.ooq6;   for   18-inch  on  the  Astoria  water-works  ;/ was  found 


HYDRAULICS.  221 

to  be  .00985,  and  c  to  be  132.88  when  F  was  3.605;  and 
for  i4-inch  pipe  n  was  found  to  be  .0107  to  .011,  and  c  to  be 
as  follows: 

Velocity  in  Feet  Corresponding 

per  Second.  Value  of  c, 

0.7  102 

1.2  III 

1.5  112 

An  assumption  of  n  =  .010  is  that  generally  made,  and 
seems  to  accord  well  with  experiments. 

(30)  For  riveted  pipe  with  butt-joints  and  countersunk 
rivets  the  coefificient  c  would  probably  be  a  little  less  than  for 
wood-stave  pipe,  or  n  a  little  greater,  on  account  of  the 
tendency  of  the  coating  to  pucker  or  form  rugosities;  when 
the  rivets  are  not  countersunk  the  velocity  will  be  still  less; 
and  when  lap-joints  are  used  the  coefficient  diminishes  with 
the  thickness  of  the  plates.  For  the  16- inch  Astoria  pipe, 
having  plates  .134  to  .log  inch  thick,  c  was  found  to  be 
112.3  when  V  was  4.58,  and  ;/  was  ,011.  This  value  was 
also  obtained  by  Hamilton  Smith  for  a  similar  pipe.  For  the 
East  Jersey  Water  Company's  pipe  4  feet  in  diameter,  with 
plates  0.25  to  0.375  inch  thick,  n  averaged  0.0148.  For  a 
wrought-iron  riveted  pipe  at  Holyoke,  Mass.,  8^  feet 
diameter,  with  plates  0.36  inch  thick,  ;/  was  found  to  be  .016. 
At  Portland,  Ore.,  ;/  was  found  to  be  .0115;  and  c  for 
42-inch  pipe,  plates  .203  to  ,375  inch  thick,  was  116;  for 
35-  and  33-inch,  plates  .203  inch  thick,  c  was  127  and  123 
respectively. 

The  above  formulas  and  coefficients  are  applicable  only 
to  uniform  flow  over  an  uninterrupted  surface;  and  the  /i 
used  is  that  lost  in  friction  only,  and  not  the  total  head. 
Where  water  enters  a  pipe  there  is  a  loss  of  head  due  to  the 
contraction  of  the  vein ;  a  loss  occurs  in  passing  curves,  partly 
closed  gates,  sudden  contractions  and  expansions  of  area;  and 


222  WATER-SUPPLY  ENGINEERING. 

a  part  of  the  head  is  used  in  creating  the  velocity.  That  is, 
the  total  H  existing  between  a  free  water-surface  and  any 
point  in  a  connected  pipe  is  divided  up  into  several  parts 
having  different  functions;  or 

(31)  H=  K  +  hp^K  +  hf-\-K  +  /^«; 

in  which  ht  is  the  head  lost  at  the  entrance,  hf  is  that  lost  in 
friction,  h^  that  lost  in  curves,  and  //„,  all  other  miscellaneous 
losses. 

(32)  The  velocity  of  water  flowing  in  any  closed  conduit 

is  equal  to  V2g/i^,  in  which  /i^  is  that  portion  of  the  total  head 

on  this  point  not  consumed  in  overcoming  friction  or  other 

resistance    above    this    point,    nor    existing  as  pressure  (//^). 

I' 
This  head  is  called  the  velocity  head,  and   equals  — .     The 

2g 

heads  h^,  hf,  h^,  and  //„,  are  lost  for  any  practical  use,  being 

transformed  into  heat,  but  //„  and  hp  are  interconvertible  and 

can  both  be  utilized  as  work. 

If  water  passes  through  an  opening  cut  in  a  plate,  having 
perfectly  sharp  inner  edges  and  so  formed  that  the  water  does 
not  touch  the  plate  after  passing  these  edges,  such  a  hole  is 
called  a  standard  orifice.  In  passing  through  such  an  opening 
the  vein  of  water  decreases  in  section  for  a  short  distance, 
and  this  contraction  is  called  the  "contracted  vein."*  In  the 
case  of  a  circular  opening  the  area  of  the  smallest  section  is 
about  .62  of  the  area  of  the  orifice,  or 

(33)  The  coefficient  of  contraction  c  is  0.62.  The  velocity 
in  this  section  is  about  .98  of  the  theoretical  velocity,  or  the 
coefficient  of  discharge  is  .98  of  0.62,  or  0.61.  For  a  short, 
straight  tube  projecting  into  a  reservoir  and  having  sharp 
edces  at  its  inner  end 

(34)  The  coefficient  of  discharge  c^  =  0.50; 

*  See  Appendix  B. 


HYDRAULICS.  223 

but  if  the  tube  is  four  or  more  times  its  diameter,  we  find 

U5)  ^.,  =  0.72; 

and  if  a  tube  be  fitted  in  front  of  a  standard  orifice  of  the 
same  diameter,  we  find 

(36)  Ci  —  Q.Z\6, 

The  head  lost  by  the  contraction  is 

I  \F* 

-  —  ij — , 


(37)  K  =\-^-^] 


which    ranches   in  value   from  o  to   .03 — ,   beinsf  ."iO^ —  for 
case  (36). 


By  (26)  we  find  /i/  = 


(38)  4  = 


2gd' 

baV 


180  X   2g' 


in  which  a  is  the  angle  of  curvature,  and  b  has  the  following 
values  for  different  diameters  of  pipe  d,  and  radii  of  curvature 
R  (according  to  Weisbach) :  * 

For  — =  0.2        o.^        0.6        0.8         i.o        1.2        1.4        1.6        r.8        2.0 
A 

^  =  0.131     O.13S     0.153     0.206     0.294    0.440    0.661     0.977     1.40S     1.978 

(39)  When  a  gate-valve    is    partly  closed,   the  lost  head 
due  to  this  also  is  a  function  of  — ,  or  k—,  in  which,  if  the 

2g  2g 

proportion  of  the  vertical  centre-height  of  the  opening  to  the 
diameter  of  the  pipe  be  called  (9,  according  to  Weisbach* 

when  0  =  1  i  I  I  7  f  i  i 

^  =  0.0         0.07         0.26         o.Si  2.06  5.52  17.00         97.8 

But  these  values  were  deduced  from  experiments  on  small 
valves  only. 

*  See  Appendix  B. 


224  WATER-SUPPLY  ENGINEERING. 

J.   W.    Smith,   in   1894,   found   the   discharge   through   a 
'30-inch  gate-valve  to  be  as  follows: 

Proportional  height  of  gate  0.125  0.250  0.375  0.500  0.625  0-750  0.875   i.ooo 

area  of  opening  0.125  0.287  0.443  0-593  0.729  0.851  0.946  i.ooo 

■'  discharge  0.086  0.178  0.274  0.384  0.533  0.734  0.936   i.ooo 

(40)  From  (^37),  (26),  (38),  and  (39), 

V/      '     ^     '     180     '  '  ^2£-  ' 

in  which  w  is  a  factor  representing  all  miscellaneous  losses. 


(41)  Also  Fr-       ^  ^^^ 


I        fl       ba 
O     '   ^    '    180    '         ' 


If  the  pipe  is  long,  with  few  bends,  and  gates  all  open — 
the  ordinary  condition — most  of  these  factors  may  be  neg- 
lected, as  insignificant  compared  with  — ,  and  the  equations 
reduce  to  (15)  and  (16). 

—  v 

(42)  Since  F=  ^  \^rs,  and  r  =  -^,  if  c  were  constant  the 
^  c  s 

velocity  in  two  pipes  at   the  same  grade  would  vary  as  the 

square  roots  of  their  diameters,  and  their  diameters  as  the 

square  of  the  velocities,     c,  however,  is  not  constant,  and  it  is 

found  that  V  varies  almost  exactly  as  the  j\  power  of  s,  and 

s  as  the  -y-  power  of  V. 

(43)  If  in   Fig.  21  a  pipe  AB  connect  two  reservoirs,  but 

be  closed  at  B,  the  water  in  each  of  the  pipes  CE,  GL,  and 

HK  will  stand   on   a  level  with  the  water-surface,  c,   by  (2). 

There  will  be  at  6^  a  pressure  equal  to  0.4346"^,  and  at  // a 

pressure  O.A^'iy^HK.      If  i?  is   opened,    the   pressure   head   at 

that  point  will  be  DB  only;  at  E  it  will  be  EC  minus  the  lost 

V 
head  h.  and   also  — ,  or  EM.      If  a  line  connect  M  and  D, 

2Z 


HYDRAULICS. 


225 


cutting  GL  at  F  and  HK  at  /,  the  pressure  head  at  G  is  GF, 
and  at  H  is  ///;  and  the  heads  LF  and  AY  have  been  lost  in 
overcoming  friction  above  the  points  G  and  H  respectively. 
The  line  AIFID  is  called  the  hydraulic  gradient.     The  dis- 


FiG.  21. — Hydraulic  Gradient. 


tance  of  this  at  any  point  below  the  level  of  the  upper  reser- 

V         fl  V"- 
voir  is  the  sum  of  — ,  Ji,,  —.  — ,  and  any  other  lost  head  /i„, 
2g      '     d  2g  ^  *"' 

when    /  is    the    distance    from  the   reservoir  to   the   point   in 

question,  measured   along  the  line  of  pipe.      If  the   pipe   is 

straight  and   uniform   in   bore  throughout,  MD  is  a  straight 

line.      If    the    pipe    rise   at    any    point    above    the    hydraulic 

gradient,  the  pressure  head  there  becomes  negative  and  the 

pipe  is  called  a  siphon.      The  water  between  this  point  and 

the   outlet   tends  to   run    more   rapidly  than   that  above   the 

siphon ;  but  it  can  do  so  only  if  air  be  sucked  in  through  leaks 

in   the   siphon   or   find  its   way  up   from  the   outlet.      If  this 

happens,  the  pipe  above  the  siphon  still  flows  under  pressure, 

but  that  below  it  as  an  open  conduit;   and  the  pipe  ceases  to 

act  as  a  siphon. 

(44)   If  the  pipe  were  of  larger  diameter  at  //than  at  G, 

the   velocity    F,    and   consequently    — ,  would    be    less,    and 

-A 

hence  AY  would  be  less  than  it  is.  If,  on  the  contrary,  there 
were  a  contraction  of  the  section  at  //,  KI  would  become 
greater,  and  might  cause  the  pressure  head  HI  to  become 
minus,  or  a  vacuum  to  exist  at  H. 

In  Fig.  22,  B" L"  is  a  pipe  with  numerous  changes  of  sec- 
tion,   and    an    orifice   at  L" ,    fed   by  a  reservoir  with  a  free 


226 


WATER-SUPPLY  ENGINEERING. 


surface  at  X,  XL'  being  a  horizontal  line  at  the  level  of  this 
surface.  XBCD  .  .  .  L  is  the  hydraulic  gradient  of  this  line. 
WB'  is  the  head  lost  at  entrance.  IVB  is  the  velocity  head. 
CC  —  BB'  is  the  head  lost  in  friction  in  the  pipe  B" C" . 
BB"  is  the  pressure  head  at  B"  \   CC"  is  the  pressure  head 


Fig.  22. — Hydraulic  Gradient,  Compound  Pipe. 


at  C" \  CV=  BIV  is  the  velocity  head  in  this  section — a 
constant  since  the  velocity  must  be  constant.  C'V  —  B'W 
=  CC  —  BB'.  D'U  —  C'V=  head  lost  by  sudden  expan- 
sion  at  CD".  E' T —  D' U  ^  friction  head  lost  in  the  pipe 
D" E" ,  which  is  less  per  foot  than  that  in  B"C" ,  and  hence 
the  angle  between  UT  acad  XL'  is  less  than  that  between  IVV 
and  XL'.  The  velocity  is  less  in  D" E"  than  in  B"C",  and 
hence  DU\s  less  than  CV.  At  E"F"  is  a  slight  increase  in 
friction  head  due  to  the  contraction,  and  the  velocity  head 
FS  becomes  equal  to  CV,  and  SR  is  parallel  to  \VV.  At 
G" H"  is  a  gradual  increase  of  section  and  no  loss  of  head 
except  the  friction  head,  which,  like  the  velocity,  gradually 
becomes  less,  and  RQ  is  a  curved  line.  QP  is  parallel  to 
UT,  and  HQ  =  IP  =  TE.  At  //  is  a  gradual  contraction 
and  increase  of  velocity,  and  PO  curves  downward  as  the 
friction  per  foot  increases  and  consequently  the  angle  between 
PO  and  XL';  and  for  a  similar  reason  ON  curves  in  the 
opposite  direction.  0/ is  large  since  the  pipe  aty"  is  very 
small,  and  //  varies  as  F'  and  hence  inversely  as  d*.  Part  of 
L"L  is  lost  at  the  orifice  L"  and  part  is  added  to  Jl/L  in 
creating  additional  velocity  for  the  jet  at  L". 

The  line   WVU  .    .   .   M  must  continually  fall,   since  at 


H  YD  RA  UL ICS.  2  2  7 

every  point  some  head  is  being  consumed  in  friction  and 
cannot  be  used  again.  (It  is  of  course  not  destroyed,  but  is 
transformed  into  heat  which  cannot  be  utilized  by  ordinary 
practical  methods.)  The  total  head  between  this  and  the 
pipe  equals  pressure  head  plus  velocity  head,  and  either  of 
these  can  be  partly  or  wholly  converted  into  the  other  or  into 
friction  head  or  work  at  any  point,  as  is  illustrated  in  Fig.  22. 
At  any  point  the  total  head  H  at  that  point  can  be  accounted 
for,  and  if  all  the  divisions  of  H  but  one  be  known,  this  one 
must  be  the  difference  between  H  and  the  sum  of  the  others. 
Thus,  at  G",  H=  G'G";  G'R  =  K,  or  WB' ,  plus  the  head 
lost  in  friction  up  to  that  point.  If  it  be  desired  to  know 
this,  we  have 

h,  =  H-{Ji,-^RG^GG"\ 

V 
in    which  RG,    the   velocity  head,    =  — :    and    GG''  is    the 

2^ 

pressure  head  and  can  be  measured  by  a  pressure-gauge. 

(45)  A  piezometer  is  a  small  pipe  so  attached  to  a  water- 
pipe  that  its  bore  is  normal  to  the  direction  of  flow  in  the 
pipe,  and  the  bore  of  the  pipe  is  left  smooth  and  continuous 
except  for  the  orifice  itself.  Any  internal  pressure  will  then 
force  water  out  of  this  orifice;  and  if  a  vertical  glass  tube  be 
attached  to  the  small  piezometer-pipe,  water  will  rise  in  this 
to  balance  such  pressure,  or  as  high  as  the  hydraulic  gradient. 
A  piezometer  should  be  placed  only  where  the  flow  is  parallel 
to  the  barrel  of  the  pipe.  For  instance,  in  Fig.  22  it  should 
not  be  placed  between  C"  and  D'\  where  there  are  eddies. 

(46)  After  a  jet  issues  from  an  orifice  it  cannot  be  under 
pressure,  and  hence  all  the  head  not  lost  must  be  utilized  in 
producing  velocity — must  be  transformed  into  the  energy  of 
a  moving  stream.  It  is  found  that  about  2^  of  the  head 
existing  at  the  orifice  as  pressure  head  is  lost  here,  and  98^ 
appears  as  additional  velocity  at  the  contracted  vein. 


228  WATER-SUPPLY  ENGINEERING. 

(47)  The   path   of  a  jet  emerging  freely  from  a  vertical 
orifice  is  a  parabola,  whose  equation  is 

_  ^ 

in  which  y  and  x  are  coordinates  of  any  point  in  the  path, 
from  the  orifice  as  a  centre  of  coordinates.  If  the  orifice  is 
inclined,  the  formula  becomes 

x"  sec'  e 


y 


=  X  tan  Q  — 


aK 


in  which  B  is  the  angle  made  with  the  vertical  by  the  plane 
of  the  orifice. 

(48)  By  the  above  formulas  and  tables  the  head  lost  by 
the  flow  in  any  pressure  conduit  or  any  part  thereof  can  be 
found,  when  this  flow  is  uniform.  In  a  distribution  system, 
however,  water  is  being  removed  from  the  pipes  at  more  or 
less  uniform  intervals  of  distance,  and  hence  the  velocity  and 
head  lost  per  foot  of  length  continually  diminishes.  If  we 
assume  that  the  same  amount  of  water  is  being  discharged  at 
uniform  intervals  along  a  length  of  pipe,  the  head  lost  in 
friction  in  a  given  length  due  to  such  discharge  is  practically 
one  third  of  that  which  would  be  lost  if  the  discharge  all 
occurred  at  the  end  of  this  section;  and  if  there  is  also  a  flow 
from  the  end  of  the  section  under  consideration  the  lost  head 
is  equal  to  the  above  plus 

f-dV'^:^-)^   °^  ^^^ =-^3^ -27+ -^7/^—2^ T' 

in  which  /  is  the  length  of  section  considered,  d  the  diameter 
of  the  pipe,  V  the  velocity  due  to  the  flow  at  the  lower  end 
of  this  section,  and  V -\-  v  that  due  to  the  flow  at  the  upper 
end. 

(49)  If,  while  water  is  flowing  through  a  pipe,  a  gate  be 


HYDRAULICS. 


229 


closed  instantly,  the  momentum  of  the  moving  water  will 
produce  an  impulse  upon  the  gate  and  by  transmission  upon 
all  parts  of  the  pipe.  This  is  called  water-hammer.  If  the 
water  were  an  inelastic  bar,  the  impact  would  equal  the 
weight  of  the  entire  moving  column  of  water  times  the 
square  of  the  velocity.  Since  it  is  not,  but  the  forward  par- 
ticles are  somewhat  compressed,  an  interval  of  time  is  con- 
sumed in  bringing  all  the  energy  of  the  moving  water  to 
bear  upon  the  gate.  Moreover,  as  each  elementary  section 
of  water  presses  against  the  one  in  front  it  presses  sideways 
with  the  same  intensity,  and  the  pipe  yields  to  this  pressure, 
and  in  doing  so  absorbs  part  of  the  energy.  But  the  pipe 
returns  to  its  normal  size,  and  this  and  the  elasticity  of  the 
water  cause  a  reflex  pressure-wave  back  from  the  valve, 
which  pressure-wave  travels  back  and  forth  along  the  length 
of  the  pipe  until  the  energy  is  absorbed  in  the  friction  of 
water  and  iron  molecules  among  themselves  and  against  each 
other.  Thus  a  high- pressure  wave  may  pass  through  a  pipe 
a  dozen  or  more  times,  becoming  less  each  time,  before 
becoming  inappreciable. 

From  experiments  made  at  Cornell  University  in  1892-3 
upon  the  effect  of  the  sudden  closing  of  a  ^-inch  tap  on  the 
end  of  a   i^-inch  pipe,  the  following  results  were  obtained. 


Static  pressure , 

Number  of  distinct  blows 

Maximum  pressure 

Minimum  "  

Time  pulsations  continued,  in  seconds 
Pressure  at  end  of  one  second  ... 
Ratio  of  increase  of  pressure 


With  Air-chamber. 

No  Air- 
chamber. 

- 

2. 

29-5 

8 
72.5 

2-5 

0.8 
36 
2.47 

28.5 

8 
61.5 
10 

0.8 
34-5 

2.15 

27-5 

9 
69.0 
16 

1  + 
36 

2.56 

Air- 
chamber 
filled 
with 
Water. 


28 

9 

76. 

9 
I. 

36 
2. 


70 


During  one  set   of   experiments  there  was  an  air-chamber  a 
short    distance    above    the    tap;     during    another     this    was 


230 


WATER-SUPPLY  ENGINEERING. 


removed;  and  during  the  third  it  was  filled  with  water.      The 
time  of  closing  the  tap  was  about  y^^  of  a  second. 

Experiments  were  also  conducted  in  a  2-inch  pipe  with  a 
2-inch  gate-valve  suddenly  closed  by  a  lever.  From  these 
the  curves  in  the  following  diagram  were  obtained.      From 


;     y  M   1   :  1  '   ; 

'Z        ''X- 

-                                                          -^4          ^1 

.      V                     J. 

'  ^=,z        Jv 

X-1               t 

•&-  ^             ci^ 

ife        ^2 

"nn                                                                       ^^y                   ^t^ 

-?■-  >^  XI            ^**^  ^ 

'■^l                o-^^ 

n       2                   .-3 

j?<^         c^ 

^^         A 

^^      4?< 

v,'^^    -,,v,2*^    _                ^i.* 

?■           "oi^                     ►f'^^ 

100                   -    -?■&-      ^^?'=^      -         3»»!^^"' 

-i                   ,.^^                               ,'    r       2"^ 

^'-      ^^=           ^,    ^;i' 

-■"■  y'^ ^'■''     j2»  ii-"' 

rf  ^              —■"""' 

- 

0  1  2  3  4  5  6  7  8  9  10 

VELOCITY  IN  PIPE, FEET  PER  SECOND. 

Fig.  23. — Water-ram  in  2-inch  Pipe. 

this  it  is  seen  that  a  pressure  of  300  lbs.  was  given  by  water- 
ram  due  to  a  velocity  of  8  feet  per  second  when  no  air- 
chamber  was  used. 

No  satisfactory  formula  for  calculating  water-ram  has  yet 
been  advanced ;  but  it  is  probable  that  the  force  varies  as  the 
square  of  the  velocity,  directly  as  the  speed  of  closing  the 
gate,  and  as  some  root  of  the  length  of  moving  water-column. 
It  also  probably  increases  in  a  piping  system  with  the  number 
and  nearness  of  dead-ends.  (See  Proceedings  Am.  Soc. 
C.  E.,  vol.  XIV;  Mechanics  for  August,  1884;  a  paper  by 
Prof.  Church  in  the  Journal  of  the  Franklin  Inst,  for  1890; 
a  description  of  the  above  experiments  by  Prof.  R.  C. 
Carpenter  in  the  Transactions  of  the  Am.  Soc.  of  Mechanical 
Engineers;  and  Trans.  Am.  Soc.  C.  E.,  vol.  XXXIX.  pages 
1-17.) 


HYDRA  ULICS. 


231 


Art.  64.     Flow  in  Hose,  Nozzles,  etc. 

The  loss  of  head  in  fire-hose,  nozzles,  fire-hydrants,  and 
similar  appliances  follows  the  same  general  laws  as  that  in 
pipes,  with  a  difference  in  coefficients  only.  The  following 
tables,  from  experiments  by  Freeman,  give  what  are  probably 
the  most  reliable  coefficients  obtained  for  hose  and  nozzles. 

Table  No.  53. 
jets  from  smooth  nozzles.     (preeman.) 

MAXIMUM    VERTICAL    AND    HORIZONTAL    DISTANCES    TO    WHICH    JETS    WILL     BE 
THROWN    BY    THE    PRESSURES    INDICATED. 


10 
20 
30 
40 
50 
60 
70 
80 
90 
100 


From  ^-inch  Nozzle. 


Height 
in  Feet. 


20 
40 

59 

78 

93 
104 
114 
123 
129 
134 


17 
33 
43 
60 
67 
72 
76 
79 
81 

S3 


JQ.E 


72 


136 
153 
^67' 


a 


52 
73 
90 
104 
116 
127 
137 
147 
156 
164 


From  i-in 

ch  Nozzle. 

Height 
in  Feet. 

Horizontal 
Distance 
in  Feet. 

Discharge  in 
Gallons 
per  Minute. 

A 

B 

21 
43 
63 
83 
lOI 

117 
130 

140 

147 
152 

18 
35 
51 
64 
73 
79 
85 
89 
92 
96 

77 
133 

1S9 
205 

93 
132 
161 
186 
208 
228 
246 
263 
279 
295 

From  114-inch  Nozzle. 


Height 
in  Feet. 


22 

44 
66 
86 

107 

126 
140 

150 
157 
161 


19 

37 
53 
67 
77 
85 
91 
95 
99 

lOI 


C  C  1) 


;q.s 


83 
148 
186 
213 
236 


.2  0  a 


14S 
209 
256 
296 
331 
363 
392 
419 

444 
468 


Column  A  gives  the  average  height  reached  by  the  highest  drops  in 
still  air;  B,  the  maximum  height  at  which  an  effective  fire-stream  is  fur- 
nished. The  horizontal  distances  are  those  reached  by  the  furthest  drops 
in  still  air,  at  the  level  of  the  nozzle;  the  stream  being  effective  for  fire 
purposes  for  only  about  half  this  distance. 

Table  No.  53, 

FRICTION    FACTOR,  /,    IN    2^-INCH    HOSE. 

Velocity  in  feet  per  second.. .  .   f  =      4 
For  unlined  linen  hose /  =  0.038 

"     rough  rubber-lined  cotton  /"  =  0.030 

"    smooth  "  "        /=  0.024 

Discharge  in  gallons  per  minute   =     61 


(freeman.) 


6 

10 

15 

20 

0.038 

0.037 

0.035 

0.034 

0.031 

0.031 

0.030 

0.029 

0.023 

0.022 

0.019 

0.018 

92 

153 

230 

306 

232  WATER-SUPPLY  ENGINEERING. 

(50)  The  diagram,  Plate  XIII,  shows  the  pressure  head 
corresponding  to  given  quantities  of  discharge  through  ordi- 
nary, best-quality  2-|^-inch  rubber-lined  fire-hose  and  smooth 
nozles;  this  including  both  head  lost  in  friction  in  the  hose 
and  that  necessary  to  produce  the  increased  velocity  in  the 
jet.  The  column  headed  "  Open  Butts"  is  for  hose  alone; 
the  others  for  the  length  of  hose  indicated,  and  nozzle  of  the 
size  indicated  by  the  column  heading.  Thus  500  feet  of  hose 
with  a  i^-inch  smooth  nozzle  attached  would  require,  to  dis- 
charge 200  gals,  a  minute,  a  pressure  at  the  upper  end  of  the 
hose  of  a  little  over  64  lbs.  or  about  150  feet  pressure  head; 
while  the  same  discharge  with  the  nozzle  detached  would 
require  a  pressure  head  of  about  1 10  feet. 

(The  velocity  of  flow  in  a  2^-inch  hose  equals  the  dis- 
charge in  cubic  feet  divided  by  .034.)  The  head  lost  in 
mill-hose  is  about  twice  as  great  as  that  given  in  the  table; 
and  that  lost  in  unlined  hose  about  2.3  times  as  great. 

(This  diagram  is  slightly  modified  from  one  prepared  from 
Freeman's  experiments  by  Mr.  Ernest  Stenger  and  published 
\n  Engineering  Nezvs,  Feb.  10,  1898.) 

(51)  The  head  lost  in  fire-hydrants  will  naturally  vary 
with  the  hydrant  used,  and  these  vary  materially  in  design. 
The  only  important  tests  of  fire-hydrants  known  to  the  author 
are  those  made  by  Mr.  Charles  L.  Newcomb  at  Holyoke, 
Mass.,  in  1897-8  and  described  in  a  paper  read  before  the 
Am.  Soc.  of  Mechanical  Engineers  in  May  1899.  He  found 
the  friction  loss  in  some  hydrants  to  be  four  times  as  great 
as  that  in  others.  The  loss  when  discharging  500  gals,  per 
minute  through  two  hydrant-butts  or  nozzles,  with  a  pressure 
of  30  lbs.,  is  shown  in  the  diagram  on  page  234. 

The  total  loss  is  seen  to  be  from  0.78  to  2.5  lbs.,  or  1.8 
to  6  feet  head.  The  loss  in  passing  the  nozzle  is  seen  to  be, 
in  some  hydrants,  many  times  that  in  the  barrel;  a  mechani- 
cal defect  which  could  and  should  be  remedied. 


HYDRAULICS. 


233 


000 


000 


_i § 


00000  ooc 


Plate  XIII. — Fire-stream  Diagram  for  Ordinary,   Best   Quality,  2^ 
INCH  Rubber-lined  Hose. 


234 


WATER-SUPPLY  ENGINEERING. 


In  the  fall  of  1893  Dexter  Brackett  found  the  friction  loss 
in  a  post-hydrant,  6|  inches  inside  diameter,  6-inch  rubber 
valve,  4^-inch  nozzles  or  outlets,  to  be  4  lbs.  for  a  discharge 
of  500  gals,  per  minute,  and  16  lbs.  for  looo  gals.,  a  large 
proportion  of  this  loss  being  at  the  nozzle-valve. 


No. 


Name. 


Beaumont 

Chapman,  gate 

3-way 

4-way 

Coffin,  gate . . . 

compression  . 
Corey,  4  inches      . . . 

"      5  inches 

Glamorgan,  4  inches 


«  o 


•o  O  3 
2>U 


390 
435 
425 
734 

577 
580 
467 
506 
418 
560 
531 


No. 


Name. 


Holyoke,  gate,  4  in.  barrel 
"     6i" 

"         compression 

gate,  si  in 

"         gate,  4-way 

"  "     6-way 

Ludlow 

Mathews,  5  inches 

"        4-way 

Pratt  and  Cady 


356 
500 

66q 
538 
580 

497 
750 
757 


•0   0  3 


1 .02 
3.16 

1.20 

0.77 

2,34 

1.87 

1.42 

1-5° 
2.28 


TWO  NOZZLES  DISCHARGING  250  GALS.  PER  MINUTE  EACH 

Fig.  24. — Friction  Losses  in  Fire-hydrants. 


Art.  65.  Measurement  of  Water. 
For  many  purposes  it  is  desirable  to  measure  the  amount 
of  water  which  is  flowing  in  a  natural  or  artificial  channel  or 
pressure  conduit.  The  above  formulas  enable  approximations 
to  be  made  when  the  head  and  the  character  and  dimensions 
of  the  conduit  are  known,  and  when  this  is  uniform  in  cross- 
section.  More  accurate  methods  are  needed,  however,  in 
many  instances. 


HYDRAULICS. 


235 


Small  quantities  of  water  can  be  caught  in  a  pail  or  barrel 
and  measured  or  weighed,  the  latter  being  generally  the  more 
accurate.  Or  an  orifice  can  be  used,  preferably  a  circular 
one.  For  larger  quantities,  weirs  can  be  placed  in  the 
stream;  or  for  either  small  or  medium  amounts  in  pressure- 
conduits  meters  can  be  used.  For  large  streams  the  only 
practicable  method  used  is  to  obtain  the  velocity  at  different 
points  in  a  cross-section  of  known  area,  by  the  use  of  floats 
or  current-meters. 

The  weight  of  pure  water  varies  with  its  temperature. 
The  following  table,  by  Hamilton  Smith,  gives  the  weight 
of  distilled  water. 

Table  No.  54. 

WEIGHT    OF    DISTILLED    WATER    PER    CUBIC    FOOT. 


Temperature, 

Weight  in 

Temperature, 

Weight  in 

Temperature, 

Weight  in 

Degrees. 

Pounds. 

Degrees. 

Pounds. 

Degrees. 

Pounds. 

32 

62.416 

85 

62. 169 

155 

61. 106 

34 

62.420 

90 

62.118 

160 

61.006 

36 

62.422 

95 

62.061 

165 

60.904 

33 

62.423 

100 

61.99S 

170 

60.799 

39-3 

62.424 

105 

61.933 

175 

60.694 

40 

62.423 

no 

61.865 

180 

60.586 

45 

62.419 

"5 

61.794 

185 

60.476 

50 

62.40S 

120 

61.719 

190 

60.365 

55 

62.390 

125 

61.638 

195 

60.251 

60 

62.366 

130 

6r.555 

200 

60. 135 

65 

62.336 

135 

61-473 

205 

60.015 

70 

62 . 300 

140 

61.386 

210 

59-893 

75 

62.261 

145 

61.296 

212 

59-843 

80 

62.217 

150 

61.203 

Water  as  ordinarily  found  in  nature  weighs  somewhat 
more  than  this:  .05  to  .20  lbs.  for  river-water,  and  1.5  to  1.8 
lbs.  for  sea-water.      Ice  weighs  about  57.2  to  57.6  lbs. 

(52)  In  using  circular  orifices  the  head  is  measured  from 
the  centre  of  the  orifice  to  the  water-surface  above.  The 
back  of  the  orifice  plate  should  extend  as  a  plane  for  at  least 
three  times  the  diameter  of  the  orifice  on  all  sides  of  the 
same,  and  the  area  of  the  reservoir  should  be  so  much  larger 


236 


WATER-SUPPLY  ENGINEERING. 


than  that  of  the  orifice  that  there  is  practically  no  velocity  of 
the  water  therein,  or  "velocity  of  approach."  The  head 
should  be  considerable  to  avoid  a  vortex,  and  to  render  errors 
in  its  measurements  proportionately  small.  The  equation 
for  discharge  through  a  circular  orifice  is 


(53)^  =  \cnd^  V2^H    .  -  -8  ^  -  r6P4^< 


4194304// 


^T^r-etc.j; 


in  which  c  is  a  coefficient,  d  is  the  diameter  of  the  orifice,  and 
H  the  total  head  upon  the  centre  of  the  same.  If  H  is  more 
than  ^d  this  equation  can  be  abbreviated,  without  reducing 
its  practical  accuracy,  to  the  form 


(54) 


q  =  Icnd^  ^2gH=6.2g2>gcd'  VH. 


The  value  of  c  for  vertical  circular  standard  orifices  differs 
with  the  head  and  diameter.  The  following  values  were 
deduced  by  Hamilton  Smith  from  the  best  experiments. 
(From  Merriman's  "  Hydraulics.") 

Table  No.  55. 
coefficient  c  for  vertical  circular  standard  orifices. 


Diameter  of  Orifice  in  Feet. 

Head 

//     — 

in  Feet. 

0.02 

0.04 

0.07 

O.I 

0.2 

0.6 

1.0 

0.4   .. 

0 

637 

0.624 

0.618 

0.6    0 

655 

630 

.618 

.613 

0.601    0 

593 

0.8 

648 

626 

.615 

.610 

601 

594 

590 

I.O 

644 

623 

.612 

.608 

600 

595 

591 

1-5 

637 

618 

.608 

.605 

600 

596 

593 

2.0 

632 

614 

.607 

.604 

599 

597 

595 

3-5 

629 

612 

.605 

.603 

599 

59S 

596 

-   3 

627 

611 

.604 

.603 

599 

598 

597 

4 

623 

609 

.603 

.602 

599 

597 

596 

6 

618 

607 

.602 

.600 

598 

597 

596 

8 

614 

605 

.601 

.600 

598 

596 

596 

10 

611 

603 

•599 

■  59S 

597 

596 

595 

20 

601 

599 

•597 

.596 

596 

596 

594 

50 

596 

595 

•594 

•594 

594 

594 

593 

100 

593 

592 

•592 

.592 

592 

592 

592 

H  YDRA  ULICS.  237 

The  limit  of  error  in  measuring  by  circular  orifices  can  by 
care  be  kept  within  i^.  Coefficients  for  square  and  rect- 
angular orifices  are  not  as  generally  reliable  as  those  for 
circular,  and  are  not  given.  Values  for  these  may  be  found 
in  Hamilton  Smith,  Jr.'s  "Hydraulics"  and  Merriman's 
"  Hydraulics." 

(55)  A  weir  is  an  upright  obstruction,  similar  to  a  dam  of 
stone  or  timber,  over  which  water  flows.  In  hydraulics,  by 
a  standard  weir  is  meant  one  in  which  the  inner  face  is  a 
vertical  plane,  and  the  edge  of  the  weir,  or  its  crest,  is  sharp 
and  similar  to  that  of  a  standard  orifice.  Weirs  are  generally 
made  rectangular,  but  are  triangular  or  trapezoidal  in  some 
cases.  The  crest  of  a  rectangular  weir  may  extend  to  the 
side  of  the  flume  or  canal  conducting  the  water  to  it,  or  it 
may  be  a  rectangular  notch  cut  in  the  weir-plate,  the  vertical 
edges  being  bevelled  similar  to  the  horizontal  one.  In  the 
latter  it  is  said  to  have  end  contractions,  in  the  former  the 
contractions  are  said  to  be  suppressed.  If  the  contractions 
are  not  suppressed,  the  weir-plate  should  extend  as  a  plane 
on  each  side  of  the  weir  a  distance  at  least  three  or  four  times 
the  depth  of  water  on  the  crest;  and  for  an  equal  distance 
below  the  crest,  whether  there  be  contraction  or  not. 

It  is  very  difficult  to  measure  the  depth  of  water  over 
the  crest,  and  instead  is  taken  the  height,  H,  above  the  crest 
of  the  surface  of  the  water  before  it  begins  to  curve  toward 
the  weir. 

The  formula  for  discharge  is 

(56)  ^  =  4  i'^/(^+  nhf  =  5.343^/(//+  «/0^; 

in  which  q  is  discharge  in  cubic  feet  per  second; 

<:  is  a  coefficient  of  discharge; 

/  is  the  length  of  crest  of  the  weir; 

n  is  a  coefficient  of  velocity  of  approach; 

V* 
h  is  the  head  of  velocitv  of  npproach  =  — . 


238  WATER-SUPPLY  ENGINEERING. 

Table  No.  56  gives  values  for  c  for  weirs  with  end-con- 
tractions and  for  those  in  which  these  are  suppressed ;  and 
for  waste-weirs  or  weir-dams  having  flat  crests. 

Francis,  from  his  classic  experiments  on  weirs  at  Lowell 
in  1854,  deduced  the  expression 

(57)  ^  =  3-33/^' 

for  weirs  with  end-contractions  suppressed,  and 

(58)  ^=3.33(/-o.2//)7/t 

for  weirs  with  two  end-contractions;   or,  allowing  for  velocity 
of  approach, 

(59)  q=-h.lll\_{H^lCf-Jf\  and 

(60)  q  =  3.33(/-  o.2H)l{H+/if  -  /.=]. 

Most  of  these  experiments  were  made  on  weirs  10  feet 
long  (all  were  quite  large  ones)  and  with  heads  ranging  from 
0.4  to  1.6  feet;  and  his  formulas  are  best  adapted  to  such 
proportions. 

(61)  For  a  trapezoidal  weir  the  coefficient  may  be  made 
constant  by  a  proper  sloping  of  the  sides.  If  this  slope 
be  made  i  :  4,  the  equation  q=  3.36///'  is  found  to  be 
fairly  exact. 

Many  designs  of  meters  are  on  the  market  which  will 
measure  the  flow  through  them  with  an  error  of  less  than  3^. 
In  most  of  these  a  revolving  or  oscillating  piston  or  diaphragm 
moves  a  registering  train  of  wheels,  the  number  of  revolutions 
being  recorded,  not  as  such,  but  as  the  number  of  gallons  or 
cubic  feet  which  trial  has  shown  must  pass  through  the  meter 
to  cause  this  number  of  revolutions. 

(62)  The  Venturi  meter  is  particularly  adapted  to  large 
pipes  and  volumes  of  flow.     It  acts  upon  the  principle  illus- 


HYDRAULICS. 

Table  No.   5G. 
coefficients  for  weirs. 

CONTRACTED    STANDARD    WEIRS. 


239 


ESective 

Head 
in  Feet. 

Length  of  Weir  in  Feet. 

0.66 

I 

2 

3 

4 

5 

7 

10 

19 

0.1 

0-15 

0.2 

0.15 

0.3 

0.4 

0.5 

0.6 

0-7 

0.8 

0.9 

I.O 

1.2 
1.4 

1.6 

0 

.632 
.619 
.6ti 
.60s 
.601 
•595 
•590 
.587 

0.639 
.625 
.618 
.612 
.608 
.601 
.596 
•593 
.590 

0 

646 

634 
626 
621 
616 
609 
605 
601 
598 
595 
592 
590 
585 
580 

0.652 
.638 
.630 
.624 
.619 
.613 
.608 
.605 
.603 
.600 
.598 
•595 
.591 
•587 
.582 

0.653 
.640 
.631 
.626 
.621 
.615 
.611 
.608 
.606 
.604 
.603 
.601 
•597 
•  594 
•591 

.65s 
.641 

•633 
.62S 
.624 
.618 
.6.5 
.6,3 
.612 
.611 
.609 
.608 
.605 
.602 
.600 

656 
642 

634 
629 
62s 
620 
6x7 

614 
613 

6t2 

6n 
610 
609 
607 

STANDARD    WEIRS,    CONTRACTIONS    SUPPRESSED. 


0.1 

0.15 

0.2 

0.25 

0-3 

0.4 

0.5 

0.6 

07 

0.8 

0.9 

1 .0 

1.2 


0.659 

•64s 
.638 
•034 

.631 

.628 

.627 
.627 

.628 
.629 
.631 
•633 
.636 

.640 

.642 

0.658 

.645 

.637 

•633 

.629 

.625 

.624 

.623 
.624 
.625 
.627 

.628 

.632 

•  634 

.637 

0.658 

.644 
.637 
.632 
.628 
.623 

.621 

.620 
.620 

.621 

.622 

.624 
.626 

.629 

.631 

0.652 

.645 
.641 

.639 
.636 

.637 

.638 

.640 

•643 
•645 
.648 

0.649 

.642 
.638 
.636 

■633 
.633 

.634 

•635 
.637 

.639 
.641 

.646 

0.647 

.641 

.636 

.633 

.630 
.630 

.630 

.631 
■633 
.635 
.637 
.641 

.644 
•647 

0.657 

.643 

•63s 

■  630 

.626 

.621 
.619 

.618 
.618 
.618 

.619 
.619 
.620 
.622 
•  623 


WASTE-WEIRS    AND    DAMS,    CONTRACTIONS    SUPPRESSED. 
(From  Francis'  formula,  q  =  3.oi///i'''.) 


0.1 

0.15 

0.2 

0.25 

0.3 

0.4 

o.s 

0.6 

0.7 

0.8 

0.9 

1.0 

1.2 

t.4 

T.6 


3.556 
•556 
.556 

•557 
■559 
.564 
.568 
•572 
■578 
.581 


3-554 
■553 
•553 
•554 
•557 
.560 
.564 
.568 
•573 
•576 
•579 
•587 


3.552 
•552 
•551 
•552 
■554 
•  558 
.561 
•564 
.569 
■572 
.576 

•583 
■  588 
•593 


^•556 
.550 
•550 
•550 
■550 
•552 
•555 
•558 
.562 
.566 
.569 
•572 
.578 
•584 
•  589 


0-555 
.550 
•550 
■549 
•548 
•550 
•552 
•555 
■558 
.562 
•  56s 
.568 
•574 
•579 
•584 


3-555 
•549 
■549 
■548 
•547 
•548 
•550 
•552 
•554 
•559 
■  561 
.564 
■569 
■574 
•578 


0-554 
■549 
■549 
•546 
■  546 
.546 
•548 
•550 
•553 
•556 
.558 
.560 
•564 
.568 
•571 


240  WATER-SUPPLY  ENGINEERING. 

trated  in  Fig.  22,  page  226,  at  J,  except  that  the  pipes  at 
both  ends  are  the  same  size.  Assuming  that  the  loss  by 
friction  in  the  meter  is  so  small  that  it  may  be  disregarded, 
we  have 

hp  +  K  =  hp  -\-  hj,      or     hp—  hp  —  h,'  —  h^ ; 

in  which  //  and  h'  are  the  head  above  the  meter  and  at  the 
throat  y  respectively.  Now /^/>. and  /z/ can  be  measured  by 
pressure-gauges  or  piezometers;  also  v  :  v'  ■=  d'  ^  :  d^,  and 
h^  :  hj  =  v''  :  t-" ;  hence 

h^  :  h:  =  d'*  :  d\     or     h^  =  ^. 

Also  K  •■  h^  -  h,  =  d"  :  d'  —  d" ;   hence 

_d'\h:  -h:) 

"  ~      d'  -  d"    ' 
Or,  substituting, 

_  d'  \hp  —  hp') 
'^--~V~-d"      ' 

in  which  d  and  d'  are  the  diameters  of  pipe  and  throat 
respectively,  and  can  be  measured. 

ad" 


q^ca  V2gh,  =  c  -  V2g{hp  —  hp') ; 

^  a   —  a 

in  which  r  is  a  coefficient  which  must  generally  be  ascertained 
by  experiment  for  each  meter,  but  is  almost  i. 

(63)  For  determining  the  velocity  of  large  streams  floats 
may  be  used,  traversing  as  long  a  stretch  of  the  stream  as 
can  be  found  of  practically  uniform  cross-section;  the  time  it 
takes  floats  in  different  positions  in  the  cross-section  to 
traverse  this  distance  being  carefully  noted.  Floats  should 
be  used  which  expose  as  little  of  their  surface  as  possible  to 
the  wind,  and  a  day  should  be  selected  when  there  is  little 
air  stirring.  A  more  accurate  method  is  to  use  a  current- 
meter,  which  consists  essentially  of  a  wheel  with  cups  upon 
its  circumference,  and  which  is  revolved  by  the  current,  the 


HYDRAULICS.  24 1 

velocity  of  revolution  depending  upon  that  of  the  current. 
Each  meter  is  rated  to  find  coefficients  by  which  to  reduce 
the  rate  of  revolution  to  rate  of  flow.  Readings  are  taken  at 
a  number  of  points  in  a  cross-section  of  known  area,  the 
greater  the  number  of  these  points  the  better. 

QUERIES. 

18.  In  Fig.  22,  if  the  pipe  have  the  diameters  given,  that  at  J" 
being  2  inches,  and  if  B" C" ,  C"F",  F" G'\  and  K" L"  be  each 
200  feet  long,  G" H"  and  /"/"  each  10  feet,  and  H" I"  and 
J" K"  each  5  feet,  the  whole  being  new  cast-iron  pipe,  what  would 
be  the  discharge  per  second  through  a  i-inch  circular  orifice  at  L" 
if  L"L'  is  100  feet? 

19.  A  valley  has  the  shape  of  an  isosceles  triangle,  3  miles  wide 
on  the  base  and  5  miles  long,  with  soil  of  clayey  loam.  If  a  dam 
be  placed  at  the  apex,  what  should  be  the  length  of  the  waste-weir 
or  spillway  to  give  a  maximum  depth  of  flow  over  it  of  3  feet  ? 
How  much  higher  than  the  spillway  should  the  top  of  the  earth 
embankment  be  ?     Use  the  rainfall  records  for  eastern  New  York. 

20.  A  Holyoke  gate  fire-hydrant,  4-inch  barrel,  two  nozzles,  is 
connected  by  10  feet  of  4-inch  pipe  to  a  6-inch  main  500  feet  long, 
which  in  turn  is  fed  by  a  12-inch  main  1000  feet  long.  What  eleva- 
tion must  the  reservoir  have  above  the  hydrant-nozzles  to  enable 
these,  both  discharging  at  once,  to  give  a  combined  discharge  of  500 
gallons  per  minute,  no  other  water  being  drawn  from  the  pipes  at 
the  same  time  .'' 


CHAPTER   XII. 
DAMS   AND    EMBANKMENTS. 

Art.  QQ.     Materials  for  Construction. 

Dams  have  been  built  of  earth,  loose  rock  ("  rock-fill"), 
timber,  iron,  and  steel,  and  of  concrete,  stone,  and  brick 
masonry;  and  cores  of  timber,  iron,  and  masonry  have  been 
used  in  many  dams  of  the  first  and  second  classes.  Of  these, 
stone  masonry  is  the  most  substantial  and  tightest,  concrete 
masonry  next,  timber  probably  comes  next  (within  the  life- 
time of  the  timber),  and  loose  rock  and  earth  last.  Iron  and 
steel  have  not  been  used  for  any  but  movable  dams,  except 
as  a  facing  or  core.  A  poorly  designed  or  constructe-l 
masonry  dam  may  of  course  be  weaker  or  more  porous  than 
a  timber  or  earthen  one;  but  the  above  order  will  hold 
generally  for  properly  designed  and  well-built  dams. 

Timber  dams  are  most  applicable  for  use  as  weir-dams — 
that  is,  those  over  whose  crests  water  flows — because  of  the 
tendency  of  the  timber  to  rot  if  alternately  wet  and  dry. 
Earth  dams,  on  the  other  hand,  will  surely  fail  if  any  water 
whatever  flows  over  them.  Rock-fill  dams  are  not  intended 
to  serve  as  weirs,  and,  although  an  occasional  small  flow  over 
their  crests  may  not  prove  fatal,  should  not  be  designed  to 
serve  as  such. 

Masonry  is  the  only  material  adaptable  to  weir-dams  of 
permanent  construction.  It  is  also  used  for  high-crest  dams 
which  are  not  intended  to  pass  water,  when  absolute  stability 

242 


DAMS  AND    EMBANKMENTS.  243 

or  tightness  is  desired,  or  when  the  height  of  the  dam  exceeds 
60  to  75  feet  (although  earth  dams  have  been  constructed 
much  higher;  as  the  Honey  Lake  Valley,  Cal.,  dam,  118 
feet  high,  with  a  puddle  core).  Earth  dams  are  practically 
adapted  to  locations  where  there  is  not  a  sufificiently  firm 
foundation  to  support  a  high  masonry  dam,  or  where  the  cost 
of  this  would  be  excessive;  as  in  the  case  of  the  Honey  Lake 
Valley  dam,  which  was  so  inaccessible  that  haulage  brought 
the  cost  of  cement  up  to  $8.25  per  barrel.  If  the  distance 
to  bed-rock  or  excessive  cost  render  the  use  of  masonry 
inadvisable  for  a  weir-dam,  a  timber  dam  is  probably  the  only 
alternative;  but  if  the  work  is  extensive,  the  dam  more  than 
40  or  50  feet  high,  or  a  permanent  construction  desired, 
masonry  must  be  used  and  carried  down  to  bed-rock  at  what- 
ever depth. 

It  may  sometimes  be  desirable,  for  financial  reasons,  to 
construct  a  temporary  dam  of  timber  a  little  above  the  best 
location  for  a  masonry  dam,  and  build  a  masonry  dam  at  this 
location  some  time  within  twenty  years,  for  which  length  of 
time  a  well-constructed  timber  dam  should  be  perfectly 
sound. 

The  most  careful  consideration  of  all  the  conditions  should 
be  taken  by  the  engineer  in  deciding  upon  the  character  of  a 
proposed  dam. 

Art.  67.     Masonry  Dams.     General  Construction. 

Masonry  is  practically  not  flexible,  and  hence  a  perfectly 
inflexible  foundation  is  necessary  if  there  are  to  be  no 
unknown  and  unprovided-for  strains  in  the  structure  which 
may  cause  its  rupture.  Comparatively  small  and  low  dams 
may  be  set  upon  heavy  timber  foundations  resting  upon  piles 
or  a  solid  hardpan  or  gravel  foundation,  but  only  the  greatest 
care  to  prevent  undermining  of  the  foundation  and  a  large 


244 


WATER-SUPPLY  ENGINEERING. 


factor  of  safety  in  the  masonry  can  render  such  a  dam  secure. 
Close  sheet-piling  should  be  carried  entirely  across  the  upper 
end  of  the  foundation,  placed  in  a  trench  which  has  been  dug 
down  to  and  a  foot  or  two  into  hardpan  or  clay,  and  puddle 
well  rammed  into  the  trench  on  each  side  of  the  sheeting. 
The  sheeting  should  be  carried  up  two  or  three  feet  higher 
than  the  foundation  and  the  space  between  it  and  the  masonry 
filled  with  concrete  or  puddle.      (See  Fig.  25.)     The  founda- 


w//iWj/niim/w/ili!Sll 


HARD-PAN 

-Dam  on  Timber  Foundation. 


Fig.  25. 

tion  should  be  carried  down-stream  from  the  dam  for  a  dis- 
tance  at  least  equal  to  the  height  of  the  dam,  to  act  as  an 
apron  to  prevent  the  falling  water  from  undermining  the 
foundation.  At  the  end  of  the  apron  should  be  placed  sheet- 
piling  similar  to  that  already  described.  In  the  case  of  a 
weir-dam  or  spillway  a  low  dam  is  sometimes  placed  at  the 
end  of  the  apron  to  form  a  water-cushion  at  the  face  of  the 
dam. 

No  masonry  dam  more  than  10  or  12  feet  high  should  be 
placed  upon  a  timber  foundation,  but  all  such  should  be 
carried  down  to  rock.  All  loose  or  decomposed  rock  on  the 
foundation  should  be  removed,  and  if  the  rock  have  a  smooth 
top  surface  a  shallow  trench  should  be  excavated  into  it  the 
entire  length  of  the  dam,  or  the  bed  should  be  cut  in  steps, 
to  prevent  leakage  and  the  sliding  of  the  dam  on  its  bed. 
Every  square  foot  of  the  foundation  should  be  thoroughly 
cleaned  and  washed,  and  covered  with  a  thick  bed  of  mortar 
just   before   the   masonry    is    laid    upon   it;    and  the   spaces 


DAMS  AND    EMBANKMENTS.  245 

between  the  dam  and  the  sides  of  the  excavation — if  any  was 
made — should  be  cleaned  out  and  filled  with  concrete. 

The  ends  of  the  dam  should  be  carried  to  bed-rock,  if 
possible,  and  treated  as  was  the  bottom.  If  rock  does 
not  extend  up  to  the  level  of  the  crest  of  the  dam  at  its  ends, 
these  should  be  carried  some  distance  into  the  banks  to  pre- 
vent leakage  around  them,  or  tight  masonry  river-walls  should 
be  carried  for  some  distance  up-stream  from  the  dam.  The 
banks  just  below  the  dam,  if  of  earth,  must  be  protected  from 
wash  by  similar  walls  carried  for  a  short  distance  down-stream 
from  the  dam. 

If  the  dam  forms  a  reservoir,  or  it  is  desired  for  any 
reason  to  draw  off  the  water  at  any  elevation  lower  than  the 
crest,  pipes  or  other  conduits  must  generally  be  carried 
through  the  dam.  These  should  never  be  given  uninterrupted 
smooth  outside  surfaces,  but  should  be  provided  with  flanges 
or  other  projections  around  their  circumferences  to  prevent 
water  from  following  along  them  through  the  wall.  Probably 
the  best  plan  is  to  place  two  or  three  wide  flanges  around  the 
pipe  near  the  upper  face  of  the  wall  and  bed  these  thoroughly 
in  concrete,  having  first  cleaned  them  and  the  pipe  and  given 
both  a  coat  of  rich  Portland  cement-mortar.  Other  flanges 
should  be  placed  at  intervals  of  10  to  20  feet  if  the  dam 
exceed  this  thickness. 

In  some  cases  a  tunnel  is  carried  through  the  dam,  open 
at  the  lower  end,  and  terminating  at  the  upper  in  a  watertight 
•well  rising  above  the  water  surface,  in  which  tunnel  the  con- 
duits are  laid.  This  is  an  excellent  plan  for  large  dams  and 
conduits. 

In  building  a  stone  dam,  care  should  be  taken  to  break 
courses  at  every  joint;  the  masonry  being  the  most  uncoursed 
rubble,  except  the  faces,  which  should  be  broken  ashlar. 
Every  stone  and  its  bed  must  be  perfectly  clean  and  have  a 
damp  surface  when  it  is  laid,  and  all  spaces  must  be  absolutely 


246  WATER-SUPPLY  ENGINEERING. 

filled  with  mortar  or  fine  concrete.  If  a  tight  dam  is  to  be 
built  these  precautions  must  be  conscientiously  observed, 
although  it  may  be  necessary  to  discharge  half  the  masons 
during  the  first  week  to  effect  this.  The  dam  should,  as  far 
as  possible,  be  so  carried  up  that  the  top  of  the  finished 
masonry  is  at  all  times  approximately  horizontal.  All  stone 
should  be  set  by  derrick;  and  no  dressing  of  stone  done  on 
the  wall,  which  is  likely  to  disturb  or  jar  stones  already  set. 
A  dam  built  in  this  way  may  be  made  perfectly  tight  under 
any  practicable  head. 

Concrete  has  been  used  for  a  number  of  dams,  and  still 
more  have  had  a  base  of  concrete  used  to  fill  up  the  irregu- 
larities in  a  rock  foundation.  A  concrete  dam  is  considered 
to  be  more  porous  than  a  stone  dam.  To  reduce  the  porosity 
to  a  minimum  the  amount  of  cement  used  should  be  \oic  more 
than  enough  to  fill  the  voids  in  the  broken  stone  or  gravel 
used.  The  mixing  of  the  dry  sand  and  cement  and  that  of 
the  mortar  and  stone  must  be  thorough;  no  more  water  must 
be  used  than  will  bring  moisture  to  the  surface  on  ramming; 
all  surfaces  of  concrete  in  place  must  be  cleaned  of  all  dirt, 
loose  stone,  and  porous  concrete,  and  thoroughly  dampened 
and  plastered  with  mortar  before  more  concrete  is  placed 
thereon;  and  the  concrete  must  be  thoroughly  but  lightly 
rammed.  All  surfaces  of  concrete  in  place  should  be  rough 
or  irregular;  and  the  top  surfaces  of  the  finished  concrete 
should  be  kept  approximately  level.  Several  large  dams 
have  been  successfully  built  of  concrete;  as  that  at  Butte 
City,  Mont.,  120  feet  high,  and  the  San  Mateo  dam,  170  feet 
high. 

Brick  has  been  used  in  the  construction  of  a  few  dams,  as 
the  Belubula  dam.  New  South  Wales,  in  which  the  top  36 
feet  9  inches  is  of  brick,  upon  a  concrete  base  having  a  max- 
imum height  of  23   feet.      Brick  is  deficient  in  weight,  both 


DAMS  AND    EMBANKMENTS.  247 

per   unit   mass  and   per  cubic   foot,    and   is  not  generally   so 
durable  as  stone  or  concrete. 

Art.  GS.     Masonry  Dams:  Designing. 

The  cross-section  of  a  masonry  dam  is  generally  designed 
on  the  assumption  that  the  dam  is  a  rigid,  monolithic  mass. 
That  this  may  be  the  case  was  demonstrated  by  a  Minneapolis 
dam,  which,  in  February  1899,  was  revolved  about  its  toe 
as  an  unbroken  mass  through  an  angle  of  about  25°,  the  cause 
being  the  pressure  exerted  by  ice  in  the  pond  above.  This 
dam  was  18  feet  high,  12  feet  through  the  bottom,  and  535 
feet  long.  It  is  doubtful  if  a  high  dam  would  remain 
unbroken  under  such  conditions,  but  it  will  be  seen  to  be  an 
assumption  on  the  safe  side  to  base  a  design  on  this  condition. 

A  dam  may  yield  in  one  of  three  ways:  it  may  be  over- 
turned as  just  described,  or  the  part  above  any  horizontal 
plane  may  so  revolve;  it  may  slide  as  a  whole  on  the  founda- 
tion, or  any  part  may  slide  on  the  part  below  it;  or  it  may 
yield  by  crushing  of  the  masonry  or  of  the  foundation.  The 
forces  acting  are:  the  weight  of  the  masonry;  the  pressure  of 
the  water;  the  dynamic  effect  of  a  river-current,  of  waves, 
and  of  logs,  ice,  or  other  floating  solid  matters;  and  the 
pressure  of  the  wind.  The  last  can  act  upon  but  a  small  part 
of  the  rear  of  the  dam,  and  when  acting  upon  the  face  of  a 
full  dam  only  increases  its  stability.  If  the  dam  be  empty, 
wind-pressure  upon  its  face  may  have  some  effect.  The  wind 
will  not  probably  exceed  50  lbs.  per  square  foot  of  vertical 
surface.      If  we   call   it   62.5  lbs.  we  find   the  pressure   to   be 

62.5//        2      ,     , 

T-,  =  —  of  the  pressure  due  to  water  on  the  same  face, 

62.5— 
2 

//    being  the   height   of  the  dam.     The   force   of  the    blow 

WV 
delivered   by   floating  logs   or   ice   equals   .       It    is    not 


248  WATER-SUPPLY  ENGINEERING. 

probable  that  any  such  matter  will  strike  the  dam  when  there 

is  a  depth  over  the  crest  of  more  than  3  feet;  at  which  depth 

the  Velocity  of  flow  over  the  crest  will  be  about  8  feet  per 

secoi'd,   and   the   energy  of  the   moving  logs  or   ice  will   be 

W      ^ 
^bout    JF,    and   the    impulse    about   — .      This   is   somewhat 

4 

1p/ .eased,  in  case  a  floating  body  strikes  the  dam,  by  the 
friction  of  the  water,  to  an  amount  probably  not  exceeding 
25^  of  the  weight  of  the  body.  A  tree  or  log  would  not, 
therefore,  probably  strike  a  dam-crest  with  an  impulse  greater 
than  4500  lbs. ;  and  probably  a  height  of  2  feet  on  the  crest 
and  2250  lbs.  impulse  would  be  high  enough  for  most  cases. 

The  greatest  impulse  due  to  waves  will  probably  not 
exceed  3000  lbs.  per  square  foot,  since  this  was  the  maximum 
found  for  ocean  waves  by  Stevenson  at  Bell  Rock  Light- 
house, and  6100  the  maximum  of  all  his  observations. 

The  pressure  due  to  the  river-current  will  seldom  be 
appreciable  in  amount,  except  at  the  very  crest,  and  here  will 
probably  never  exceed  lOO  lbs.  per  square  foot;  it  can  hence 
be  neglected  in  practical  designs. 

The  pressure  due  to  water  will  be  62.5  times  the  area  of 

the  wetted  face,  times  the  distance  from  the  centre  of  gravity 

of  such  face  to  the  water-surface.      In  calculating  it  is  con. 

venient  to  assume  a  section  of  the  wall  one  foot  long  as  a 

62.5^/' 
unit.     The   horizontal   pressure   on   this   will   be   ,    in 

which  d  is  the  depth  of  water. 

The  weight  of  masonry  for  any  given  case  can  be  ascer- 
tained by  actual  test.  By  Table  No.  60,  page  260,  we  see 
that  the  concrete  of  the  Sweetwater  Dam  weighed  164  lbs. 
per  cubic  foot ;  and  that  of  those  for  which  the  data  are  given 
the  weight  varies  between  134  and  160  lbs.  Baker  in 
*'  Masonry  Construction  "  gives  the  following  weights  for 
masonry: 


DAMS  AND    EMBANKMENTS. 


249 


Table  No.   57. 
weight  of  masonry. 

Kind  of  Masonry.  Weight  in  Pounds 

•'  per  Cu.  Ft. 

Brickwork,  pressed  brick,  thin  joints 145* 

"  "        ordinary  quality 125 

"  "        soft  brick,  thick  joints 100 

Concrete,  best 160* 

porous 130 

Granite  orlimestonc,  well  dressed  throughout 165* 

"        *'  "  rubble,  well  dressed  with  mortar I55* 

"        "  "  "        roughly  dressed  with   mortar  150 

"        "  "  "        well  dressed,  dry 140 

"  "  "        roughly  dressed,  dry 125 

Mortar,  dried 100 

Since  dam-masonry  should  be  the  best  of  its  kind,  with  all 
joints  well  filled,  the  weights  after  which  stars  are  placed  may 
be  used:  and  160  lbs.  will  be  used  in  calculations  in  this  work. 

In   a   dam   of   rectangular  section,    Fig.   26,  if    W  is  the 

weight  of  the  masonry  and  P 

the  horizontal  pressure  due  to 

a  depth  d  of  water,  the  point 

d 
of  application  of  P  is  —  above 

the  bottom,  and  that  of  W  is 

the  centre  of  the  base,  C. 

62.5^' 
The  pressure  P,  =  ,  tends  to  cause  the  dam  to  slide, 

and   this   tendency   is  resisted    by  the    friction   between    the 

dam  and  the  base,  and   the  tendency  at  any  horizontal  joint 

is  resisted  by  the  friction  in  that  joint.      This  friction  is  equal 

to  fW,  in  which  /  is  a  friction  coefficient,  values  for  which  are 

given  in  Table  No.  58. 

If  we  assume  a  coefficient  of  .65,  the  friction  resistance 

would  be  160  X  0.65  =  104  lbs.  per  cubic  foot  of  masonry. 

In  the  above  figure,  if  d  be  10  feet  and  the  width  of  the  dam 

62.5  X  100 
be  6  feet,  the  pressure  will  be   =  3125   lbs.;    and 


-p — 


w 

0     B   C         E 

Fig.  26. — Rectangular  Dam. 


250 


WA  TER-SUPPL  V  ENGINEERING. 


the  friction  resistance  will  be  10  X  6  X  104  =  6240,  and  the 
factor  of  safety  against  sliding  will  be  2.  As  a  matter  of  fact, 
if  the  dam  be  constructed  as  described  above,  there  will  be 
no  possibility  of  sliding  except  as  a  whole  upon  a  timber 
foundation;  and  in  such  a  dam  a  timber  should  be  bolted  to 
the  foundation  in  front  of  the  masonry  to  prevent  sliding. 
(See  Fig.  25,  page  244.) 

Table   No.   58. 

COEFFICIENT    OF    FRICTION    FOR    MASONRY. 

Kind  of  Masonry.  Coefficient 

Soft  brick 0.75 

Hard  brick 0.70 

Granite,  point-dressed 0.70 

Hard  limstone 0.65 

Concrete  blocks 0.65 

Granite,  well-dressed 0.60 

Limestone  on  oak 0.40 

In  the  case  of  a  trapezoidal  dam,  P^ig.  27,  with  an  inclined 


back,   the  pressure  /*  = 


Fig.  27. — Trapezoidal  Dam 
62.5^ 


2  cos 


horizontal  pressure  is,  as  before, 


-J  (see  Art.   61,  (6));  but  the 

H 

62.5^' 


or  31.25^:/',  and  the 


friction  =  flV. 

The  tendency  to  crushing  is  due  to  a  combination  of  all 
the  pressures  named,  and  is  resisted  by  the  strength  of  the 
masonry.  This  resistance  to  crushing  is  approximately  as 
follows  in  different  classes  of  stone  when  tested  in  cubes. 


DAMS  AND    EMBANKMENTS. 

Table  No.  59. 

crushing  strength  of  cubes  of  stone. 
(Baker's  "  Masonry  Construction.") 


2SI 


Ultimate  Crushing  Strength. 

Kinds  of  Stone. 

Pounds  per  Sq.  Inch. 

Tons  per  Sq 

Foot. 

Min. 

Max. 

Min. 

Max. 

20,000 

12,000 

8,000 

7,000 

5,000 

24,000 
21,000 
20,000 
20,000 
15,000 

1440 
860 
580 
500 
360 

1730 
1510 
1440 
1440 

Granite 

Marble 

The  Strength  of  masonry,  however,  is  found  to  depend  to 
only  a  minor  degree  upon  that  of  the  stone,  but  to  be  largely 
affected  by  the  character  of  mortar  and  of  bond.  The  limits 
of  safe  pressure  have  been  assumed  as  follows  by  Baker: 

For  concrete 5  to  15  tons  per  sq.  ft. 

"     rubble lO  "  15      "      "      "     " 

"    squared  stone 15  "  20      "      "      "     " 

"     limestone  ashlar 20  "  25      "      "      "     " 

"    granite  ashlar 30      "      "      "     " 

"  The  maximum  pressure  on  the  granite  masonry  of  the 
towers  of  the  Brooklyn  Bridge  is  about  2%\  tons  per  square 
foot  (about  400  lbs.  pressure  per  square  inch).  The  maxi- 
mum pressure  on  the  limestone  masonry  of  this  bridge  is 
about  10  tons  per  square  foot  (125  lbs.  per  square  inch)." 
"  The  limestone  masonry  in  the  towers  of  the  Niagara  Sus- 
pension Bridge  failed  under  36  tons  per  square  foot  and  were 
taken  down — however,  the  masonry  was  not  well  executed." 
(Baker.) 

Comparing  these  limits  with  Table  No.  57,  we  see  that 
rectangular  walls  give  the  maximum  allowable  pressure  at  the 
base  when  having  the  following  heights: 


2 "52  WATER-SUPPLY  ENGINEERING. 

Concrete 60  to  200  feet 

Rubble., 130  "    190     " 

Squared  stone 180  "  240      " 

Limestone  ashlar 240  "   300      " 

Granite  ashlar 360      * ' 

The  effect  of  water-pressure,  however,  is  to  both  increase 
the  total  pressure  and  to  make  the  pressure  near  the  toe 
greater  than  the  mean  pressure;  and  the  above  heights  are 
not  permissible  for  rectangular  dams. 

In  Fig.   26,   page  249,  let  the  length   OC  represent  the 

weight  of  a  unit  section  of  the   dam,    and   that  of   OA   the 

water-pressure ;   then   OB,   or  R,   represents  the  resultant  of 

these  two  forces  in  both  intensity  and  direction,  the  resultant 

cutting  the  base  at  a  distance  BC  from  the  centre  of  the  base. 

d 
From  the  parallelogram  of  forces  we  see  that  W  -.  P  ^  —  \  BC, 

It  is  demonstrable  that  if  the  resultant  R  cuts  the  base  at 
a  distance  from  D  less  than  one  third  DE,  the  masonry  at  E 
is  in  tension;  or,  if  it  yields  to  tension,  the  pressure  is  dis- 
tributed over  less  than  the  whole  base;  and  when  R  passes 
through  D  the  whole  pressure  is  concentrated  at  that  point. 
When  DB  =  \DE  there  is  neither  tension  nor  compression 

2R 

at  E,  and  the  pressure  at  D  is  twice  the  mean,  or  -pTp-     If  -^ 

cuts  the  base  at  C  {P  =^  o),  the  pressure  is  distributed  evenly 
over  the  base.  In  the  last  case  the  intensity  of  pressure 
cannot  be  sufificient  to  overturn  the  dam,  or  the  factor  of 
safety  against  overturning  is  infinity.  When  R  passes  through 
D  the  dam  is  on  the  point  of  overturning,  and  the  factor  of 
safety  is  i.     The  factor  for  any  position  of  R  is 

CB 


DAMS  AND    EMBANKMENTS. 


253 


which  equals  3  when  R  is  just  at  the  limit  of  the  middle  third 
of  the  base. 

In  Fig.  27,  R  can  be  calculated  as  follows:  Draw  III  ^cv- 
pendicular  to  OA  produced;  then  Al  =  W sin  /?,  01  —  P -\- 
Wsln  A  HI=  IVcos  /?,  and 


OH=R=V{P-\-  IV  sin  fif-\-{if  cos  iiy  =  VP'-\-2PlV  sin  fi-[-  IV\ 
When  there  is  no  water-pressure  JF  alone  acts,  and  this 
must  fall  within  the  middle  thir  I  of  the  base,  or  F£  must  not 
be  less  than  ^DE. 

,  _  ,         TH'  (tan  8  —  tan  0) 
F£  =  IH  tan  /3+J//tan  t>^hT^  .^tH+Ih'U.  fiM^.O') 

and 

777'  (tan  0  -  tan  fi) 

FC  =  \H  tan  0  —  \H  tan  p  +  — ^r/  ,    ^  u^  1^ r~,~i ^  \ 

<'  ^       ^  'I    12  277+677   (tan  0 -[- tan /?) 

in  which  T'  is  the  width  of  the  crest  of  the  dam,  H  is  the 

height  of  the  dam,  and  C  is  the  centre  of  the  base.      The 

CE 
factor  of  safety  against  overturning  is  -^  when  the  reservoir 

CE 

is  empty,  and  -^  when  it  is  full. 

The  maximum  pressure  will  be 
that  due  to  the  total  force  acting, 
or  the  resultant  R,  and  in  a  plane  at 
right  angles  to  this.  If  we  conceive 
the  resultant  as  resisted  by  a  number 
of  parallel  forces,  as  in  Fig.  28,  we 
find  the  total  pressure  to  be  dis-  ^j^  28. -Maximum  Pres- 
tributed   over  an  area  DE  cos  FOB,       sure    on    a    Horizontal 

J    ^u  -t.       Joint. 

and    the    average    pressure   per   unit      •' 

area  is 

R  _   V7^-^  4-  2PW  sin  i3-{-  W 

DE  cos  FOB  ~  BE  cos  FOB 

As  an  illustration,   let  N  =  d  =  40  feet,   DE  =  30  feet, 


254  WATER-SUPPLY   ENGINEERING. 

T  =6    feet,   ^  =  io°;    P  then   equals  ^1.2; =  ;o77 

cos  10°       -^   ^' 

^6  +  3o\ 
lbs. ;   W  =  iGoy J40  =  1 1 5,200  lbs. ;  R  =  116,189  ^^s. ; 

^^r.  o  ,  ^  116,189 

FOB  =  2    28';   yrF FTT^  =  ^  =  3877  lbs.,  or  1.94 

D£  cos  FOB       29.9722        "^   '^  ^^ 

tons  per  square  foot. 
^£=|(7.053)+«.6.947)+i(6-5^gg|^j)  =  .6.076  feet 

and  FC  =  1.924; 

d—  2FE  tan  /J 

(9i^  = ^ ;     and     BF  =  OF  tan  FOB  =  0.47. 

3 

In  this  dam  the  resultant  therefore  cuts  the  base  to  the 
right  of  C,  and  the  tendency  of  the  dam  is  rather  to  revolve 
backward  than  forward,  even  with  the  full  water-pressure  on. 

If   T=o,  £>£  =  20  feet,  H  =  40  feet,  j3  =  10°,  then  P, 

^20  X  40\ 
as  before,    =  5077  lbs.;     W  =   1601 1  =  64,000  lbs. ; 

R  =  65,074;  FOB  =  4°  24';  the  maximum  pressure  =  3264 
lbs.  =  1.63  tons  per  square  foot;  FF  =  9.8  feet;  FC  =  0.2 
feet;    BF  =  o.Sg2   feet;    whence  BC  =  o.6g2   feet,   and    the 

10 
factor  of  safety  against  overturning  is  -^ —  =  14^. 

If  there  were  no  wind  and  no  other  pressure  except  that 
of  motionless  water,  a  dam  might  be  constructed  with  a 
triangular  cross-section.  But  these  conditions  never  exist  in 
practice.  Waves  or  floating  logs  may  give  a  pressure  of  3000 
lbs.  per  square  foot,  and  the  friction  at  a  joint  one  foot  from 
the  top  should  therefore  equal  this.  If  the  dam  is  not  a  weir- 
dam  this  may  be  effected  by  carrying  the  top  of  the  masonry 
above  the  highest  waves.  This  may  be  (see  page  168)  4  feet 
above  the  water-surface.      If  the  top  of  the  dam  be   10  feet 

3000 

in  width,  it  should  extend — — ^-  =  2.6  feet  above 

.70  X  10  X  160 


DAMS  AND    EMBANKMENTS.  255 

the  maximum  wave-height,  or  6  feet  8  inches  above  the  water- 
surface.  Above  the  water-surface  there  may  be  exerted  by 
waves  a  pressure  of  4  X  3000  lbs.  per  Hneal  foot,  to  resist 
which  there  must  be  a  cross-section  area  above  this  point  of 

12,000  .  ,     , 

-r-  =  107  square  feet,  which  can  best  be  obtained  bv 

.70  X    I DO  ^ 

making  the  dam  say  16  feet  wide  on  top  and  7  feet  above  the 

water-surface.     This  will  be  necessary  only  when  there  is  a 

large  sweep  of  water  above  the  dam.      For  ordinary  cases  the 

pressure  will  not   exceed   one  fifth  of  this  amount,   and   20 

square  feet   above  the  water-surface  will  be  ample,   or  say 

5    feet  wide  and  4   feet  high;   which  reduction  is  also  made 

permissible  by  the  fact  that  adhesion  of  mortar  will  offer  an 

appreciable   assistance  to    friction,   and   that  the    masonry   is 

uncoursed.      If  a  dam  is  to  act  as  a  weir,  d  (which  should  for 

this  and  all  other  cases  be  taken  at  the  highest  water  possible 

to  occur)  will  be  greater  than  //,  and   the   proper  values  for 

these  should  be  used  in  the  equations,     d  —  H  will  be  the 

depth  of  flow  over  the  crest  caused  by  the  maximum  rate  of 

run-off  (see  Art.  50).     A  weir-dam  should  have  an  area  of 

section  above  the  first  joint  below  the  crest  suf^cient  to  resist 

the  pressure  due  to  d  —  //,  and  an  impact  from  logs,  etc.,  of 

say   2500    lbs.    per  lineal   foot.      To   insure   this  the   crest  is 

generally  made  quite  broad  and  the  crest-stone  quite  heavy. 

In  addition  it  is  well  to  clamp  the  crest-stones,  or  cap-stones, 

to  each  other  and  to  the  dam  beneath  (see  Plate   XIV),  and 

also  to  incline  them  toward  the  back  of  the  dam,  to  cause  a 

glancing  rather  than  a  straight  blow  to  be  struck  by  floating 

objects. 

If  a  high  weir-dam  be  made  trapezoidal  in  section,  the 

falling  water  will  cause  considerable  shock  to  the  foundation 

and  ebullition  of  the  water,  and  tend  to   undermine  the  dam 

or  to  loosen  the  bonds  of  its  masonry  by  jarring.     To  prevent 

this,  when  the  dam  is  on  soft  rock  or  is  more  than   15  or  20 


256 


WATER-SUPPLY  ENGINEERING, 


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DAMS   AND    EMBANKMENTS.  257 

feet  high  it  is  advisable  to  curve  the  toe  concave  upward,  as 
in  the  Holyoke  Dam,  and  also  curve  the  front  of  the  crest, 
the  face-outline  thus  formed  causing  this  to  be  called  an  ogee 
dam.  For  smaller  dams  the  force  of  the  water  may  be 
broken  by  stepping  the  face  at  each  course  of  masonry,  the 
cost  of  cutting  the  face-stone  to  an  ogee  curve  being  too  con- 
siderable a  proportion  of  the  whole  cost  in  a  small  dam,  while 
the  danger  from  the  falling  water  is  very  much  less  in  low 
than  in  high  dams.  For  the  same  reason  low  dams  not 
intended  to  act  as  weirs  are  generally  made  trapezoidal  in 
section,  the  top  width  and  the  height  being  decided  upon, 
and  the  bottom  width  being  made  sufficient  to  insure  the 
stability  of  the  dam. 

For  high  dams,  of  which  the  cost  will  be  very  great,  it  is 
desirable  to  use  no  more  masonry  than  is  necessary  to  insure 
their  absolute  stability.  No  formula  which  will  enable  the  form 
of  such  a  dam  to  be  calculated  directly  has  ever  been  found  ; 
but  the  calculation  can  be  made  for  each  of  a  series  of  hori- 
zontal joints,  beginning  at  the  top  and  taken  as  close  together 
as  desired,  and  a  curve  passed  through  the  points  thus  found. 
The  conditions  are:  (i)  The  resultant  pressure  both  when 
the  dam  is  full  and  when  empty  must  be  inside  the  middle 
third  of  the  joint  and  as  near  its  limit  as  possible.  (2)  The 
length  of  joint  must  be  sufficient,  relative  to  the  area  of 
vertical  section  above  it,  to  prevent  crushing  (it  being 
remembered  that  the  maximum  pressure  is  twice  the  mean 
when  (i)  has  been  observed).  (3)  The  weight  above  any 
joint  must  be  sufficient  to  prevent  sliding.  (For  a  thorough 
theoretical  discussion  of  economic  profiles,  see  Wegmann's 
"  Design  and  Construction  of  Masonry  Dams.")  Wegmann's 
practical  profile,  closely  following  the  theoretic,  is  shown  in 
Plate  XV;  in  which  is  also  shown,  in  dotted  lines,  the  Austin 
Dam  across  the  Colorado  River,  and  the  portion  of  the  new 
Croton  Dam  serving  as  a  weir. 


258 


H^A  TER-SUPPL  Y  ENGINEERING. 


Plate  XV. — Practical  Economic  Profile  of  High  Masonry  Dam. 


DAMS  AND    EMBANA'MEiVTS.  259 

To  provide  the  greatest  amount  of  storage  possible  a  dam 
must  be  raised  to  a  level  with  the  highest  permissible  water- 
line;  but  if  a  large  amount  of  water  passes  over  the  dam,  the 
water  in  the  reservoir  will  rise  above  this  line;  and  the  crest 
must  therefore  be  lowered  to  an  elevation  as  much  below  the 
high-water  line  as  will  be  the  greatest  depth  of  flow  over  the 
weir.  Both  these  conditions  are  sometimes  met  by  placing 
on  top  of  the  weir"  flash-boards"  which  practically  raise  the 
crest  of  the  weir  temporarily.  The  use  of  these  is  not  recom- 
mended, however,  unless  they  be  made  of  such  a  strength, 
or  so  designed,  that  they  will  break  or  open  before  the  water 
rises  to  the  high-water  line. 

Dams  may  be  either  straight,  curved,  or  polygonal  in 
plan ;  each  elementary  vertical  section  being  designed  to 
resist  by  itself  all  forces  tending  to  destroy  it.  If  the  dam 
be  curved  in  plan,  however,  the  masonry  may  act  as  an  arch, 
the  ends  abutting  against  solid  bed-rock.  It  is  thought  by 
some  that  the  arch  effect  cannot  come  into  play  unless  the 
section  of  the  dam  is  too  light  to  support  itself  by  gravity. 
Very  little  is  known  of  the  law  of  strains  in  such  a  dam;  but 
that  it  can  act  as  an  arch  is  demonstrated  by  the  Bear  Valley 
and  Zola  dams  (see  Table  No.  60,  page  260),  the  former  of 
which  could  not  stand  for  a  minute  if  acting  as  a  gravity-dam 
only.  The  arch  form  undoubtedly  gives  an  additional  margin 
of  safety  to  a  dam ;  but  conservative  engineers  are  not  yet 
ready  to  include  this  in  their  calculations  as  a  definite  factor 
of  resistance  to  overturning.  In  some  locations,  as  already 
stated,  a  curved  dam  may  permit  of  a  more  economical  loca- 
tion than  a  straight  one. 

Art.  69.     Rock-fill  Dams. 

In  many  parts  of  the  Western  United  States  sites  of  pro- 
posed dams  are  at  such  a  distance  from  any  railroad,  and 
transportation  to   them  is   so  difficult,   that  a  masonry  dam 


26o 


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DAMS   AND    EMBANKMENTS.  261 

becomes  a  very  expensive  structure.  In  many  cases  there 
is,  however,  plenty  of  rock  at  or  near  the  surface,  and  narrow 
cafions  are  available  for  a  dam  site.  In  a  few  of  such  loca- 
tions dams  have  been  constructed  by  simply  depositing  rough 
stone,  as  it  was  blasted  out  and  with  no  dressing,  in  an 
embankment  of  the  desired  height,  the  stones  being  carefully 
arranged,  smaller  stones  filling  the  interstices  of  the  larger  to 
give  them  a  stable  position  and  prevent  after-settling.  The 
front  and  back  faces  are  generally  lined  with  dressed  rubble, 
dry  or  in  cement,  or  with  quarry  stone  laid  carefully  by  hand 
and  well  chinked  with  spalls.  Such  dams  are  not  expected 
to  be  absolutely  tight,  and  should  never  be  used  as  weir- 
dams.  They  are  not  adapted  to  the  construction  of  storage- 
reservoirs,  because  of  their  porosity;  but  will  generally  silt 
up  in  time  and  become  reasonably  tight. 

Since  more  or  less  water  will  find  its  way  through  a  rock- 
fill  dam  the  foundation  should  be  on  rock,  as  any  other 
material  is  liable  to  erosion  which  may  prove  fatal  to  the 
dam.  Since  the  dam  acts  as  an  embankment  without 
cohesion,  the  side  slopes  must  not  be  steeper  than  the  natural 
"angle  of  repose"  of  the  material.  This  will  generally 
require  a  slope  of  at  least  i  :  i  ;  but  it  may  be  made  |  or 
even  ^  to  i  on  the  back  when  this  is  faced  with  a  heavy,  well- 
built  wall.  In  construction  the  material  should  be  carried  up 
in  approximately  horizontal  layers,  the  middle  being  always 
kept  a  little  lower  than  the  faces;  and  the  face-stone  should 
be  kept  up  to  the  level  of  the  loose  rock.  The  greatest  care 
should  be  used  to  make  the  dam  compact  by  the  use  of  spalls 
and  quarry-chips  filling  all  crevices;  but  no  earth  should  be 
used,  except  that  clean  sand  might  to  advantage  be  sifted 
down  into  the  crevices  of  stone  already  laid.  The  faces 
should  be  of  one-  and  two-man  stone,  well  bonded  and 
chinked. 

The  back  of  a  rock-fill  dam  is  in  some  cases  made  more 


262 


WATER-SUPPLY  ENGINEERING. 


LOWER_PECOS  VALLEY,  N.M.,  DAM. 


0.0  STEEL  PLATE 


LOWER  OTAY  DAM,  WITH  STEEL  HEARJ-WALU 


BED  ROCK 

CHATSWORTH  PARK  DAM. 


CASTLETON    DAM 


ESCONDIDO  DAM,  WITH 
PLANK  FACING. 


Plate  XVI. — Rock-fill  Dams. 


DAMS  AND    EMBANKMENTS.  263 

nearly  water-tight  by  banking  earth  against  it,  as  in  the  case 
of  the  Idaho  Company's  Dam,  in  which  the  earth  is  3  feet 
thick  at  the  top  and  20  feet  at  the  bottom ;  and  the  Pecos 
Valley  dams  (see  Plate  XVI);  or  by  wooden  sheathing,  as 
in  the  case  of  the  Walnut  Grove  Dam,  in  which  two  thick- 
nesses of  3-inch  planking  were  used,  with  tarred  paper 
between.  In  one — the  Lower  Otay  Dam — an  attempt  to 
make  the  dam  water-tight  was  made  by  the  use  of  a  heart- 
wall  or  sheeting  through  the  centre  of  the  dam,  composed  of 
No.  o  to  No.  3  steel  plates,  imbedded  in  concrete  i  foot 
thick  on  each  side.  This  construction  was  carried  to  the  top 
of  the  dam,  and  to  a  masonry  foundation  on  bed-rock, 
through  its  entire  length.  The  loose  rock,  with  a  slope  of 
l|^  to  I,  was  carried  down  only  to  the  ground-surface. 

Still  another  style  of  rock-fill  dam  is  the  Castlewood 
Dam,  which  has  both  faces  of  rubble  masonry,  the  upper 
being  6  feet  thick  on  top  and  12  feet  on  the  bottom,  and  the 
lower  from  5  to  7  feet  in  thickness,  the  heart  being  dry-laid 
rubble. 

Table  61,  page  264,  gives  a  partial  list  of  rock-fill  dams. 

Art.  70.     Timber  Dams. 

Timber  dams  cannot  be  considered  as  other  than  tem- 
porary structures,  which  must  ultimately  fail  by  the  rotting 
of  the  wood;  and  they  are  seldom  very  tight.  Their  general 
construction  is  that  of  cribwork  weighted  with  stone,  and 
faced  with  planking.  They  are  placed  upon  rock  or  boulder 
and  gravel  foundations — sometimes  upon  clay  or  other  firm 
soil.  Their  chief  or  only  advantage  over  masonry  is  in  cost, 
which  will  ordinarily  be  but  one-fifth  to  three-fifths  as  great 
for  timber  dams  in  a  wooded  country. 

If  the  bottom  is  hard,  cribs  are  weighted  with,  stone  and 
sunk  directly  upon  it;  but  if  soft,  rip-rap  or  loose  stone  is 


264 


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DAMS  AND    EMBANKMENTS. 


265 


266 


WATER-SUPPLY  ENGINEERING. 


placed  over  the  bottom  at  the  site  of  the  dam  and  allowed  to 
settle  as  far  as  possible,  extending  for  some  distance  above 
and  below  the  dam,  and  when  levelled  off  the  cribs  are  sunk 


^ 

^ 
^ 


upon  this.     The  timber  is  usually  12  X  12   inches  or  larger, 
drift-bolted  together. 

A  timber  dam,    14  feet  high,   was  constructed  at    Great 
Falls,  Mont.,  in  189 1-2,  across  the  Missouri  River  (Fig.  29); 


DAMS  AND    EMBANKMENTS. 


267 


and  in  1892  and  1893  one  was  built  across  the  Merrimac 
River  at  Sewall  Falls,  497  feet  long  and  13.6  feet  high,  cost- 
ing $120,000  (Fig.  30).      Still  another  type  is  shown  in  Fig. 


Fig.  31. — Cross-section  of  Bear  River  Weir. 
(From  Wilson's  "Irrigation.") 


•E^jrfc; 


Fig.  32.— Timber  Dam  at  Butte,  Montana. 

31;  and  in  Fig.  32  one  68  feet  high  and  500  feet  long,  built 
across  the  Big  Hole  River  at  Butte,  Mont.,  in  1897-8. 


268  WATER-SUPPLY  ENGINEERING. 


Art.  71.     Earth  Embankments. 

Earth  has  probably  been  used  for  more  dams  and  embank- 
ments in  connection  with  water-works  than  all  other  substances 
combined,  and  serves  this  purpose  admirably  if  properly 
designed  and  constructed ;  but  it  can  never,  under  any  con- 
dition, be  used  for  a  weir-dam,  but  a  spillway  or  waste-weir 
must  be  constructed  in  connection  with  it.  Many  earth 
dams  have  failed,  but  in  the  great  majority  of  cases  this  has 
been  because  a  too-small  spillway  has  forced  water  to  flow 
over  the  dam.  An  earthen  dam  is  almost  never  absolutely 
tight,  a  slow  seepage  continually  carrying  a  small  amount  of 
water  through  it,  and  if  this  becomes  appreciable  in  amount 
or  velocity  the  destruction  of  the  dam  is  threatened.  The 
great  requisites  of  a  safe  earth  dam  are  that  it  shall  be  so 
compact  that  no  water  can  pass  through  it  as  a  stream,  how- 
ever fine;  and  that  there  shall  be  no  continual  smooth  sur- 
face, as  of  pipe  or  masonry,  through  it  v'hich  the  water  may 
follow. 

The  pressure  due  to  the  head  tends  to  force  water  in  a 
reservoir  through  the  earth  embankment,  and  this  is  resisted 
by  the  friction  in  the  pores.  The  greater  the  distance 
through  which  the  water  must  pass  the  greater  the  friction 
and  the  less  the  seepage.  Hence  the  bottom  of  an  earth 
dam  should  be  much  thicker  than  the  top.  At  75  or  80  feet 
the  saturation  of  the  earth  reaches  an  amount  which  some 
engineers  would  fix  as  a  limit,  although  earth  dams  have  been 
built  more  than  100  feet  high. 

The  faces  of  an  earth  dam  must  be  at  least  as  flat  as  the 
angle  of  repose  of  the  material  used :  and  this  when  the 
material  is  either  moist  or  wet.  This  angle  for  different  soils 
is  approximately  as  follows: 


DAMS  AND    EMBANKMENTS. 


269 


Kind  of  Soil. 


Earth,  dry 

"       moist. . . 

"  very  wet 
Sand,  dry 

"       moist. . . . 

"  very  wet. 
Gravel,  round  . 

'  sharp. . 


Angle  of 
Repose. 


40 
45 
32 
35 

40 

30 
30 
40 


Equivalent 
Slope. 


2  to   I 

1  to   I 

6  to  I 
4  to  I 

2  to  I 

7  to  I 
7  to  I 
2  to  I 


Coefficient 
of  Friction. 


0.84 
1.00 
0.62 
O.  70 
0.84 
0.58 
0.58 
0.84 


Weight,  Lbs. 
per  Cu.  Ft. 


90 
95 
"5 
100 
no 
125 
100 
no 


From  this  it  would  appear  that  an  embankment  of  earth 
should  be  given  a  slope  of  at  least  \\  to  i,  and  one  of  sand 
if  to  I.  To  insure  stability,  however,  and  reduce  percola- 
tion, and  to  prevent  undue  wash  of  the  banks  by  rain,  it  is 
customary  and  advisable  to  give  an  inside  slope  of  2  to  i  and 
an  outside  of  2  or  2^  to  i.  If  the  dam  is  quite  high  a  still 
greater  thickness  at  the  bottom  than  these  slopes  would  give 
may  be  desirable  to  prevent  percolation ;  also  there  is  danger 
that  the  entire  lining  of  the  inside  slope  may,  on  account  of 
its  great  mass,  slip  down  the  slope.  On  the  outside  of  a  high 
bank  the  rainfall  upon  it  gradually  collects  in  rivulets  and 
tends  to  wash  the  soil.  To  prevent  these  objectionable 
results  an  offset  or  berme  5  or  10  feet  wide  is  generally  made 
about  half-way  up  each  face  of  high  embankments. 

If  the  slope  is  less  than  2^  to  i  at  the  top  of  an  embank- 
ment more  than  40  or  50  feet  high  1*;  should  be  given  this 
slope  below  that  distance  from  the  top  on  the  inside,  and  a 
slope  of  3  or  4  to  i  on  the  outside. 

The  top  of  the  embankment  should  be  at  least  6  or  8  feet 
wide,  and  if  the  dam  is  more  than  20  or  30  feet  high  it  should 
be  10  to  20  feet  wide.  It  is  generally  made  wide  enough  to 
act  as  a  driveway.  The  embankment  should  be  carried  at 
least  a  foot  higher  than  the  highest  waves  coincident  with  the 
highest  water — about  3  to  6  feet  above  high  water,  depending 
upon  the  length  of  the  reservoir.     The  elevation  above  high 


270  IVATER-SUrPLY  ENGINEERING. 

water  should  also  be  at  least    18   inches  plus  the  depth  to 
which  frost  reaches. 

On  the  outside  berme,  gutters  should  be  placed  to  catch 
the  drainage  from  the  upper  slope,  and  d r:\ins  to  lead  to  the 
toe  of  the  dam. 

In  the  above  the  embankment  has  been  considered  to  be 
of  uniform  homogeneous  material.  In  many  embankments, 
however,  a  core-wall  is  carried  through  the  middle,  con- 
structed of  masonry  or  water-tight  puddle;  and  in  others  a 
water-tight  lining  of  puddle  or  concrete  is  placed  on  the  face 
of  the  embankment.  In  the  latter  case  the  bank  is  supposed 
to  offer  stability  only  and  need  not  be  water-tight;  in  the 
former  that  portion  of  the  bank  outside  the  core-wall  is  for 
stability  only,  that  inside  assists  in  preventing  percolation. 
When  a  core-wall  is  provided  the  outer  slope  need  not 
generally  be  flatter  than  2  to  i. 

While  a  core-wall  is  made  as  tight  as  possible,  and  in 
many  cases  is  used  for  this  purpose  only,  its  chief  value 
ordinarily  is  to  prevent  woodchucks,  muskrats,  crawfish,  and 
other  digging  animals  from  making  openings  through  the 
bank.  Some  engineers  object  to  the  use  of  a  core-wall, 
claiming  that  since  it  and  the  remainder  of  the  dam  are  not 
homogeneous  cracks  will  open  between  during  settling,  to  the 
weakening  of  the  dam.  It  is  undoubtedly  true  that  a  com- 
paratively water-tight  dam  may  be  made  of  uniform  material 
throughout,  and  one  perfectly  safe  from  all  but  the  boring  of 
animals,  and  small  reservoirs  may  very  properly  be  so  built. 
But  for  large  dams  or  those  whose  rupture  would  be  attended 
with  great  damage  or  loss  of  life,  the  author  would  wish  to 
use  a  masonry  core-wall ;  and  he  would  not  recommend  a 
puddle  core-wall  except  to  secure  tightness  where  there  could 
be  obtained  only  a  small  amount  of  clay  or  other  puddling 
material.  The  masonry  core-wall  may  be  of  stone,  brick, 
or  concrete.      It  need  not    be   heavy   enough   to   resist  any 


DAMS  AXD    EMBANKMENTS. 


271 


considerable  pressure,  this  being  sustained  by  the  embank- 
ment. 

Not  only  should  a  dam  be  tight  itself,  but  it  should  be 
upon  a  water-tight  foundation — rock,  hardpan,  or  a  thick 
clay  stratum.  If  water  work  under  a  dam  through  a  soil 
subject  to  erosion,  a  cavity  will  be  created  which  will  sooner 
or  later  cause  the  destruction  of  the  dam.  A  seamy  rock 
may  permit  the  passage  of  water  under  or  around  a  dam 
without  endangering  its  stability;  but  this  is  undesirable 
because  of  the  loss  of  water,  and  the  dam  may  be  destroyed 


SCALE  OF  FEET 

Fig.  33. — Oak  Ridge  Reservoir  Dam. 


thereby;  as  was  a  dam  at  Roanoke,  Va.,  in  1888.  In  the 
latter  case  the  crevices  should  be  sought  out  and  filled  with 
concrete  or  stone  masonry;  or  it  may  be  necessary  to  build  a 
masonry  wall  as  a  lining  to  the  seamy  sides  of  a  reservoir. 

If  the  rock  or  hardpan  at  the  bottom  of  the  valley  is 
covered  with  porous  material — as  is  generally  the  case — this 
should  be  removed  and  the  embankment  founded  on  only 
solid,  continuous  impervious  material.  If  the  previous  sur- 
face material  is  quite  deep  and  the  dam  high  this  may  require 
the  excavation  of  an  enormous  amount  of  material.  Thus  a 
dam  40  feet  high,  top  10  feet  wide,  side  slopes  2  and  2^  to 
I,  will  have  a  bottom  width  of  190  feet  (the  San  Leandro 
Dam  has  a  bottom  width  of  700  feet),  and  if  10  feet  of  soil  be 
removed  this  will  require  the  excavation  of  70  cubic  yards 
per  running  foot  of  bank.     To  avoid  the  great  expense  and 


272 


WATER-SUPPLY  ENGINEERING. 


delay  occasioned  by  this,  a  puddle  or  masonry  cut-off  wall  is 
generally  carried  to  the  impervious  stratum,  and  continued 
as  a  core-wall,  if  such  be  used,  or  stopped  a  few  feet  above 
the  base  of  the  embankment  if  no  core-wall  be  used;  or,  if  a 
lining  be  given  to  the  dam,  the  cut-off  wall  is  placed  under 
and  joined  to  the  foot  of  this  lining  (see  Fig.  36,  page  275). 
The  Oak  Ridge  Reservoir  Dam  of  the  East  Jersey  Water 
Company  (Fig.  33)  is  a  good  illustration  of  a  dam  with  a 
concrete  core  (or  heart)  and  cut-off  wall. 

Not  only  the  bottom  but  also  the  ends  of  a  dam  must 
make  an  impervious  union  with  the  natural  soil.  For  this 
purpose  the  core-wall  should  be  carried  to  bed-rock  at  the 
ends  of  the  dam  if  the  rock   rise   there  above  the  water-level; 


Fig.  34. — Reservoir  M  Dam  ;  New  York  Water-supply. 

or  for  some  distance  into  the  bank  if  it  do  not.  Or,  if  there 
be  no  core-wall,  the  embankment  should  be  extended  until 
it  reaches  an  impervious  material,  or  for  a  distance  into  the 
sides  of  the  valley  equal  to,  say,  10  feet  plus  half  its  height  if 
no  impervious  material  be  found  short  of  this. 

Almost  every  character  of  soil  has  been  used  for  embank- 
ments: and  there  are  few  from  which  a  reasonably  good 
embankment  cannot  be  made.  Probably  the  best  material  is 
a  sandy  loam  with  a  small  amount  of  clay  intermixed,  and 
the  worst  is  micaceous  clay.  Contrary  to  a  wide-spread 
opinion,  clay  is  not  a  good  material  for  embankments  in  any 
but  small  quantities.     A  tough    clay  it  is  difificult — almost 


DAMS  AND    EMBANKMENTS.  27$ 

impossible — to  get  into  a  compact  homogeneous  mass;  if  wet 
it  cracks  open  on  drying  out;  and,  most  serious  of  all,  if  the 
smallest  trickle  of  water  once  finds  passage  through  it,  a  few 
minutes  suffice  to  enlarge  this  into  a  break,  so  rapidly  does 
it  dissolve  in  running  water.  An  embankment  of  clay  is 
often  tighter  at  first  than  one  of  any  other  material,  but  the 
danger  of  its  rupture  increases  with  age.  A  bank  containing 
a  large  amount  of  gravel  or  sand,  on  the  other  hand,  may 
leak  at  first,  but  becomes  tighter  and  stronger  with  age.  A 
reservoir  embankment  16  feet  high,  built  of  fine  sand,  with 
slopes  of  i^  to  I  covered  with  loam,  has  been  found  to  suffer 
no  appreciable  leakage.  Gravel  as  taken  from  the  bank, 
consisting  of  stones,  sand,  and  loam,  makes  an  excellent 
embankment  material.  "  Gravel  capable  of  being  puddled 
will  do  anything  that  clay  was  ever  used  for  in  water-works 
practice,  and  will  do  it  better"  (Clemens  Herschel).  Hard- 
pan,  the  most  impervious  soil-mixture  found  in  nature,  con- 
tains a  large  proportion  of  gravel. 

If  the  following  materials  are  obtainable,  they  may  be 
used  to  advantage  in  the  proportion  given,  to  make  an  excel- 
lent puddle,  the  amounts  here  given  furnishing  one  cubic 
yard: 

Coarse  gravel f  cubic  yard 

Fine  gravel  or  coarse  sand |      "         ** 

Fine  sand •§•      "         " 

Clay  or  loam ^     "         * ' 

These  materials  should  be  thoroughly  mixed,  the  clay 
being  broken  up  or  cross-cut  into  fine  pieces,  made  slightly 
damp,  spread  in  6-  to  9-inch  layers,  and  thoroughly  rammed, 
or  rolled  with  grooved  rollers.  If  the  gravel  and  sand  retain 
their  natural  moisture  no  water  should  be  used  in  the 
material.  Embankment  material  is  seldom  wet  too  little, 
often  too  much.     Natural  hardpan,  if  broken  up  and  rolled 


274 


IV A  TER-SUPPL  Y  ENGINEERING. 


dry,  will  make  a  tight  dam  if  water  be  admitted  behind  it 
slowly,  the  clay  taking  up  water  by  capillary  attraction  and 
swelling.  Puddle  should  never  be  made  wet  enough  to 
quake,  as  it  would  then  be  porous  upon  draining  or  drying 
out. 

During  construction  al)  surfaces  coming  into  contact 
should  be  rough.  The  ground  upon  which  the  dam  is  built 
should  be  stripped  of  all  the  soil  which  is  porous  or  contains 
roots  or  other  vegetable  matter,  and  then  ploughed  or  spaded 
up,  that  the  new  and  old  material  may  unite;  also  the  top 
surface   of    the    embankment   should    be   rough   when    more 


STRATUM      OF      IMPERVIOUS      CLAY 


Fig.  35. — Honey  Lake  Valley  Dam. 

material  is  placed  upon  it,  and  the  rollers  used  should  be 
grooved.  An  earth  embankment  should  never  be  placed 
upon  rock,  unless  a  masonry  core-wall  be  used  and  carried 
down  3  feet  or  more  into  the  bed-rock,  as  a  water-tight  joint 
cannot  be  made  between  earth  and  a  smooth  rock-bed. 

In  building  up  the  embankment  the  centre  should  be  kept 
somewhat  lower  than  the  faces;  and  these  should  extend  one 
or  two  feet  beyond  the  line  of  the  finished  bank  and  afterward 
be  trimmed  off,  since  the  edge  of  a  bank  cannot  be  properly 
compacted.  No  large  stones,  sticks,  roots,  or  any  matter 
which  can  decay  should  be  permitted  in  an  embankment.  If 
the  material  needs  wetting,  this  might  better  be  done  before 
the  fresh  layer  is  put  on,  rather  than  after;  the  bond  between 
the  fresh  and  old  material  being  thus  made  more  thorough, 
and  the  material  being  less  liable  to  cling  to  the  roller. 


DAMS  AND    EMBANKMENTS. 


275 


Nothing  should  extend  through  the  dam  when  this  can 
be  avoided,  and  any  pipe  or  other  conduit  which  must  pass 
through  it  should  be  furnished  with  a  number  of  flanges  and 
other  projections,  or  if  of  masonry  should  be  left  as  rough  as 
possible;  and  the  best  of  puddle,  mixed  and  rammed  with  the 
greatest  care,  should  surround  it.  Where  possible  it  is 
ordinarily  better  to  place  the  spillway  or  the  overflow-pipe 
(which  may  be  used  if  the  reservoir  is  small  and  does  not 
receive  drainage  direct)  at  one  end  of  the  dam  on  the  natural 
soil;  or  the  overflow-pipe  and  the  conduit  may  be  carried  in 
a  tunnel  which  passes  through  the  dam  and  terminates  at  its 
upper  end  in  a  tight  inlet-tower,  as  in  the  case  of  a  masonry 


HARD  PAN 

Fig.  36. — Puddle-lined  Reservoirs. 


dam.  Such  a  tunnel  should  be  in  every  case  carried  down 
to  bed-rock  throughout  its  length.  If  a  pipe  or  conduit  be 
carried  through  the  embankment  it  should  rest,  not  on 
masonry  piers  12  feet  apart — a  construction  too  often 
adopted,  to  the  endangering  of  the  pipe  by  breaking  between 
supports — but  upon  bed-rock  or  hardpan,  or  a  continuous 
foundation  of  the  roughest  possible  masonry  in  cement-mortar 
carried  down  to  rock  or  other  firm  bottom,  and  provided  with 
projecting  or  cut-off  walls  to  prevent  water  from  following 
the  masonry  through  the  dam.  Next  to  insufficient  spill- 
ways, improperly  built  conduits  through  embankments  have 
been  the  cause  of  the  greatest  number  of  ruptures  in  earth 
dams. 

Where  there  is  a  masonry  waste-weir  in  the  centre  of  the 


276 


WA  TER-SUPPL  Y  ENGINEERING. 


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Q       (Al       (/2 

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E 
c 

C 

Q 

(i 

) 

DAMS  AND    EMBANKMENTS.  2JJ 

dam    it   is   an   excellent   plan  to  carry  all  pipes  or  conduits 
through  this,  as  was  done  at  No.  5,  Boston  Water-works. 

Table  No.  62  gives  the  data  of  only  a  few  earth  dams,  as 
an  illustration  of  general  practice. 

Art.  7-2.     Hydraulic  Dam-construction. 

Two  or  more  dams  have  been  constructed  in  California  by 
what  is  known  as  the  hydraulic  metliod,  one  of  which.  La 
Mesa  Dam,  is  "  66  feet  high,  251.5  feet  thick  at  the  base, 
and  20  feet  wide  at  the  top,  the  materials  for  which  were 
transported  and  deposited  in  place  by  flowing  water,  by  the 
process  known  to  miners  as  'ground-sluicing,'  the  surplus 
water  from  the  flume  (the  San  Diego  Flume)  being  used  for 
this  purpose  and  at  the  same  time  stored  in  the  reservoir  as 
it  was  being  formed  back  of  the  dam."  "The  volume  of 
material  handled  was  38,000  cubic  yards,  which  had  to  be 
brought  an  extreme  distance  of  2200  feet,  and  stripped  from 
an  area  of  11.5  acres  to  a  mean  depth  of  2  feet.  .  .  .  The 
water  used  was  from  300  to  400  miner's  inches — 6  to  8 
second-feet.  .  .  .  From  the  main  ditch  at  various  points 
laterals  were  carried  down  the  slope  of  the  hill  toward  the 
dam  on  a  grade  of  6^0,  dividing  the  ground  into  irregular 
zones  of  50  to  lOO  feet  in  width  by  several  hundred  feet  in 
length,  reaching  back  to  the  top  of  the  ridge.  In  sluicing, 
these  divisions  were  stripped  off  clean  to  bed-rock,  beginning 
next  to  the  dam  and  working  back  to  the  head  ditch,  the 
w'ater  being  carried  along  the  upper  side  of  the  strip  to  the 
lower  side  across  the  end  of  the  division  where  the  ground- 
sluicing  was  progressing. 

"  The  fall  from  the  upper  line,  or  clear- water  ditch,  to 
the  lower  side  of  the  zone  was  as  great  as  the  slope  of  the 
ground  would  admit  of — the  greater  the  fall  the  more  rapid 
the  sluicing.  The  work  done  was  highly  satisfactory  as  long 
as  this  slope  was  not  flatter  than  about  i  in  4.  .  .  .    As  the 


278 


WA  TEH-SUP  PL  V  ENGINEERING. 


stream  secured  its  load  of  earth  and  gravel  it  was  conveyed 
along  the  line  of  the  tower  ditch  by  24-inch  wooden-stave 
pipes  until  deposited  on  the  embankment.  .  .  .  The  pipes 
were  found  to  wear  very  rapidly,  and  were  lined  first  with 
strips  of  wood  and  then  with  strap-iron  or  tire-steel.  Cast- 
iron  pipe  is  found  to  be  preferable  for  this  sort  of  service. 
...  It  is  apparent  that  an  embankment  built  in  this  manner 
is  compacted  as  thoroughly  as  it  could  be  by  any  process  of 
rolling,  and  is  not  subject  to  further  settlement.  It  is  also 
manifest  that  the  finer  materials  are  by  this  process  precipi- 
tated in  the  interior  of  the  fill,  and  that  the  particles  are  in 
a  general   way  graded  in  size  from  the  outside   toward    the 


/        ^    !  r  t i 

--yi. TiT^'S ^  -25-  -^  -"- -  §.*i!e-*Jioi7e8— 


Fig.  37. — La  Mesa  Dam.     Hydraulic  Construction. 

centre."  (See  Fig.  37.)  (From  "Reservoirs  for  Irrigation," 
by  James  D.  Schuyler,  in. the  U.  S.  Geological  Survey  Report 
for  1896-97.) 

It  is  evident  that  the  localities  where  this  construction  is 
possible  are  limited  in  number. 


Art.  73.     Reservoir  Lining. 

Storage-reservoirs  are  seldom  less  than  an  eighth  of  a 
square  mile  in  area,  and  it  would  ordinarily  be  impracticable 
to  line  or  cover  these;  and  the  lining  is  not  often  necessary 
to  secure  tightness,  since  the  reservoir  is  in  most  cases  formed 
bj'  a  dam  across  a  narrow  valley,  which  dam,  or  its  core-wall, 


DAMS  AXD    EMBANKMENTS.  279 

can  be  carried  as  a  cut-off  wall  to  rock  or  clay  on  both  bottom 
and  sides. 

A  distributing-reservoir,  however,  is  more  frequently 
constructed  on  a  mountain  side  or  top,  and  is  built  largely  or 
wholly  by  excavation  and  embankment.  This  construction 
will  in  many  cases  produce  a  reservoir  which  is  porous  on  the 
sides  of  the  excavation;  and  on  the  bottom  also,  if  rock  or 
hardpan  is  not  reached.  Such  a  reservoir  will  require  either 
that  a  core-wall  carried  down  to  clay  or  rock  entirely  surround 
the  excavation,  or  that  the  reservoir  be  lined  with  some  im- 
pervious material. 

When  rock  occurs  over  the  entire  bottom  of  the  reservoir 
or  a  considerable  portion  of  it,  it  is  practically  impossible  to 
render  this  tight  by  any  material  other  than  masonry,  either 
as  a  lining  or  core-wall.  Since  the  latter  would  call  for  a 
trench  excavated  to  rock  entirely  around  the  reservoir,  the 
masonry  is  in  most  if  not  in  all  cases  placed  as  a  lining.  If 
the  excavation  extends  for  any  distance  into  rock,  the  face 
of  this  is  ordinarily  made  vertical;  and  the  earth  should  be 
faced  with  a  water-tight  retaining-wall,  since  it  is  apt  to  slip 
on  the  rock-surface.  Such  a  construction  is  shown  in  Fig.  38, 
page  281,  a  section  of  the  Manchester,  N.  H.,  high-service 
reservoir.  The  bottom  may  be  left  unlined  if  the  rock  has 
no  seams  and  is  perfectly  smooth;  but  it  will  generally  be 
advisable  to  give  it  a  lining  of  concrete — from  6  to  12  inches 
if  to  prevent  leakage;  otherwise  sufficient  to  level  off  the 
surface  and  render  easier  the  drawing  off  of  all  the  water  and 
the  cleaning  of  the  reservoir.  The  retaining  wall  should  be 
practically  water-tight;  but  is  generally  backed  with  earth  to 
add  to  the  imperviousness  and  stability,  and  should  therefore 
be  capable  of  retaining  this  without  overturning  when  the 
reservoir  is  empty. 

When  rock  forms  the  bottom  of  the  reservoir  but  is  not 
excavated  at  all,  the  earth  may  be  given  a  slope  of  i^  to  i  if 


28o  WATER-SUPPLY  ENGINEERING. 

only  8  or  lo  feet  deep,  but  should  be  2  to  i  if  15  or  more 
feet  deep.  The  use  of  clay  puddle  for  a  lining  to  such  a 
reservoir  might  be  adopted,  but  cannot  be  recommended  as 
always  satisfactory,  concrete  being  a  safer  material  for  both 
bottom  and  sides.  Embankment  which  is  to  be  lined  should 
be  compacted  with  particular  care,  and  but  a  small  amount 
of  water  used  in  the  material. 

A  reservoir  entirely  in  earth  may  be  lined  with  either  con- 
crete or  clay.  If  the  former  be  used  the  bottom  should  be 
thoroughly  rolled  with  heavy  rollers  to  compact  it ;  and  a 
layer  of  gravel  spread  before  rolling  will  be  of  assistance  ia 
securing  this  condition.  If  the  bottom  be  of  clay,  this  treat- 
ment will  often  make  an  artificial  hardpan  which  will  be  as 
good  as  a  clay  puddle.  If  hardpan  be  reached  in  the  bottom 
it  will  ordinarily  be  necessary  merely  to  level  this  off  and  roll 
it  with  a  heavy  flat  roller.  If  no  clay  or  hardpan  be  reached 
a  puddle  lining  is  advisable.  This  may  be  mixed  in  propor- 
tions of  clay,  I  part,  sand  and  fine  gravel,  i  part,  and  coarse 
gravel,  2  parts.  This  should  be  put  on  in  4-inch  layers  and 
thoroughly  rolled,  the  total  thickness  being  i  to  3  feet, 
depending  upon  the  depth  of  water.  This  should  be  pro- 
tected in  some  way  from  penetration  by  fish,  etc.,  wash  of 
water,  and  injury  during  cleaning  of  the  reservoir.  Six 
inches  or  so  of  gravel,  with  dry  walls  on  the  slopes,  is  often 
used  for  this  purpose;  but  a  better  lining  is  made  of  4  to  8 
inches  of  concrete. 

Clay  lining  is  now  seldom  used  for  embankments,  because 
the  lining  is  apt  to  slip  and  to  be  loosened  by  frost,  to  crack 
open  if  alternately  wet  and  dried,  and  to  break  if  a  settlement 
occurs  in  the  bank;  and  because  the  same  amount  of  puddle 
can  generally  be  used  to  better  advantage  as  a  heart-wall. 
A  small  reservoir  on  porous  soil  may  require  to  be  lined 
throughout,  and  in  this  case  a  puddle  bottom-lining  may  be 
used  and  continued  either  as  a  slope  lining  or  as  a  heart-wall 


DAMS  AND    EMBANKMENTS. 


281 


(see  Fig.  36,  page  275).      Clay  lining  should  always  be  pro- 
tected from  injury;   that  on  the  slopes,  by  masonry. 

Additional  tightness  has  been  secured  when  vertical  walls 
are  used,  by  building  practically  two  walls  around  the  reser- 
voir, one  outside  the  other,  and  with  a  narrow  annular  space 


Fig.  38. — Reservoir  in  Rock  Excavation,  Manchester,  N.  H. 

between  them  which  is  filled  with  rich  Portland  cement- 
mortar,  with  or  without  the  admixture  of  fine  stone  or  gravel. 
Asphalt  has  been  used  as  a  lining  in  many  Western  and 
a  few  Eastern  reservoirs,  being  placed  upon  concrete  or 
directly  upon  the  earth  embankment.  "  The  natural  proper- 
ties of  asphalt  seem  to  render  it  a  useful  material  from  which 
to  form  a  water-tight  coating  for  reservoirs.  It  is  insoluble 
in  water,  and  neither  acids  nor  alkalis  dissolve  it  or  affect  its 
cohesion;  hence  it  imparts  no  taste  or  color  to  water  coming 
in  contact  with  it.  It  is  elastic  and  will  yield  to  a  consider- 
able settlement  of  the  surface  on  which  it  lies  without  cracking 
or  losing  its  integrity.  It  is  easily  repaired,  and  new  material 
can  be  made  to  unite  perfectly  with  the  old,  wherever  a  patch 


282  WATER-SUPPLY   ENGINEERING. 

may  be  needed."  (Jas.  D.  Schuyler,  Trans.  Am.  Soc.  C.  E., 
vol.  XXVII.  page  629.)  Trouble  was  experienced  in  the  earlier 
use  of  asphalt  because  of  its  tendency  to  flow  on  the  side 
slopes,  more  particularly  above  the  water-surface  when  ex- 
posed to  the  hot  sun.  It  is  thought  that  this  difficulty  has 
been  overcome  in  more  recent  practice  by  use  of  the  proper 
grades  of  material.  "The  first  coat  should  be  liquid  asphalt, 
so  called,  which  has  great  penetrating  qualities,  enters  fully 
into  the  foundation-soil  and  takes  root,  so  to  speak.  This 
coating  has  great  adhesive  qualities  which  are  of  great  value, 
but  on  the  other  hand  it  is  utterly  lacking  in  ability  to  stand 
the  sun's  heat. 

"  The  second  coat,  the  sun-proof  coat,  should  consist  of 
hard  rock  asphalt  heated  up  to  300°  F.  and  applied  hot. 
This  coating  is  both  water-proof  and  sun-proof,  but  is  utterly 
lacking  in  adhesive  qualities,  and  were  it  not  for  the  first  coat 
underneath  could  be  taken  up  readily  like  a  carpet."  (L.  J. 
Le  Conte,  in  Trans.  Am.  W.  W.  Ass'n,  June,  1896.) 

Asphalt  has  also  been  used  to  give  elastic  or  expansion 
joints  between  sections  of  concrete  lining,  as  in  the  Astoria, 
Ore.,  Water- works  Reservoir,  the  bottom  lining  of  which 
was  formed  of  6  inches  of  concrete,  f  inch  of  mortar,  and  a 
coat  of  asphalt,  the  concrete  being  made  in  20-foot  sections 
joined  by  asphalt,  which  served  its  purpose  admirably,  the 
desirability  of  its  use  being  shown  by  a  change  of  f  inch  in 
the  width  of  joints  under  various  temperatures.  Such  expan- 
sion joints  are  desirable  in  large  continuous  surfaces  of  con- 
crete, since  the  coefficient  of  expansion  of  this  is  practically 
the  same  as  that  of  iron;  that  is,  a  sheet  200  feet  long  would 
change  about  an  inch  and  a  quarter  in  length  if  the  range  of 
temperature  were  80°  F. 

Another  method  of  using  asphalt  is  illustrated  by  the  side 
lining  of  this  reservoir,  which  was  formed  of  concrete  coated 
with  asphalt,  and  covered  with  a  layer  of  brick  dipped  in  hot 


DAMS   AND    EMBANKMENTS.  283 

asphalt  and  laid  flat,  a  final  coating  of  asphalt  being  given  to 
the  whole. 

In  southern  California  a  dam  has  been  lined  with  concrete 
formed  of  broken  stone  (all  grades  including  dust  being  used) 
and  asphalt,  and  this  construction  would  seem  to  offer  some 
advantages.     (See  Trans.  Am.  Soc.  C.  E.,  vol,  XXXV.  p.  70.) 

In  the  East,  asphalt  has  been  used  for  rendering  tight 
defective  reservoirs  at  Philadelphia  and  at  Payson  Park, 
Boston,  both  originally  lined  with  concrete,  and  has  proved 
satisfactory  for  this  purpose. 

Art.  74.     Covered  Reservoirs. 

An  impounding-reservoir  is  of  such  size  as  to  render  a 
covering  impracticable,  and  distributing-reservoirs  only  have 
been  covered.  Covering  is  most  frequently  desired  when  the 
supply  is  from  ground-water,  which  is  so  often  given  an 
objectionable  taste  by  the  presence  of  alga.  By  using 
covered  reservoirs  the  water  is  delivered  to  the  consumer 
without  having  been  at  any  time  exposed  to  the  light,  with- 
out which  very  few  algae  can  exist.  A  covering  is  also  desir- 
able to  exclude  dust  and  other  atmospheric  impurities  and  to 
prevent  malicious  pollution;  also  to  protect  the  water  from 
heat  and  maintain  a  uniform  temperature  and  to  prevent  loss 
by  evaporation.      A  covered  reservoir  should  be  ventilated. 

The  covering  may  be  of  timber,  metal,  or  masonry.  The 
former  is  generally  the  cheaper  but  least  satisfactory.  It  is 
generally  constructed  by  resting  horizontal  beams  upon 
timber  or  iron  posts  or  brick  piers,  the  beams  being  spaced 
equally  over  the  entire  area  of  the  reservoir  and  covered  with 
plank.  For  small  reservoirs  but  40  or  50  feet  in  diameter  an 
ordinary  circular  wooden  roof  has  been  used,  covered  with 
tin  or  slate.  For  somewhat  larger  reservoirs  steel  roof  con- 
struction has  been  used.     This,  however,  offers  little  protec- 


284 


WATER-SUPPLY  ENGINEERING. 


tion  from  the  sun's  heat.  At  Quincy,  111.,  a  reservoir  415 
by  317  feet  was  covered  with  timber  by  the  first  method  (see 
Fig.  39).  At  Pasadena,  Cal.,  five  reservoirs  are  covered  with 
timber  roofs;  the  largest,  330  by  540  feet,  using  2-inch  iron 


pipe  for  posts  and  4"  X  10''  X  18'  girders.  No  snow  falls 
in  this  climate;  but  the  weight  of  this  must  be  considered  in 
designing  roofs  in  Northern  localities. 

A  roof  of  brick  or  concrete  masonry  is  generally  covered 


DAMS   AND    EMBANKMENTS. 


285 


with  earth  to  protect  it  from  accident  and  to  assist  in  exclud- 
ing the  heat  of  the  sun.  Such  a  covering  in  the  form  of  a 
circular  dome  was  used  on  a  50-foot  circular  reservoir  at 
Coshocton,  Ohio,  the  roof  costing  $779.  At  Brookline  and 
Wellesley,  Mass.,  arches  resting  on  masonry  piers  were  used, 
the  arches  being  groined  elliptical  in  the  latter  (see  Fig.  40); 


Coane  Oravef, 
.        loam,  d'fhick:  6'thick- 


'Ventilator 


Sodded 


Manhole, 

Iron  Frame  and  Cover. 


\EI.3I5.I 


er= 


Half  Vertical  Section. 

Fig.  40. — Covered  Reservoir,  Wellesley,  Mass. 
{Eh^.  Neivs,  vol.  XXXVIII.) 

and  in  the  former,  covering  arches  were  supported  by  brick 
piers  and  connecting  arches  or  lintels.  The  latter  plan  was 
also  adopted  at  Hudson,  Wis.,  the  covering  arches  being  of 
hollow  tile,  however,  instead  of  brick.  Hollow  tile  was  used 
at  Waltham,  Mass.,  also  for  a  dome  covering. 

A  reservoir  was  constructed  at  Boise  City,  Idaho,  in  1891, 
by  tunnelling  into  a  sandstone  mountain  for  a  depth  of  125 
feet,  the  tunnel  being  20  feet  wide,  7  high,  and  plastered 
with  i  to  i^  inches  of  cement-mortar;  a  covered  reservoir  for 
artesian  well-water  being  thus  formed.  This  method  is  of 
course  applicable  to  few  localities. 

QUERIES. 

21.  Describe  fully  the  purpose  of  each  detail  of  construction 
shown  in  Fig.  25. 

22.  A   dam   of  granite   rubble  masonry  has  a  vertical  up-stieam 


286  WATER-SUPPLY  ENGINEERING. 

face,  is  trapezoidal  in  section,  is  5  feet  wide  on  top,  20  feet  wide  on 
the  base,  and  is  35  feet  high.  What  are  the  factors  of  safety  against 
overturning  and  sliding  when  water  flows  2  feet  deep  over  the  crest  ? 
What  is  the  maximum  pressure  per  square  foot  on  the  foundation  ? 
What  thickness  of  base  must  a  concrete  dam  have,  its  height  and 
crest-width  being  as  before,  to  give  the  same  factor  of  safety  against 
overturning? 

23.  If  the  Bear  Valley  Dam  (see  Table  60)  has  a  trapezoidal 
section  and  vertical  up-stream  face,  and  were  resisting  the  water- 
pressure  by  gravity  alone,  where  would  the  resultant  cut  the  base 
when  water  was  flowing  i  foot  deep  over  the  dam  ?  How  high  could 
the  water  rise  above  the  foundation  before  the  resultant  would  move 
out  of  the  middle  third  of  the  base  ? 


CHAPTER    XIII. 
PURIFICATION   OF   WATER. 

Art.  75.     General  Methods. 

The  aims  of  purification  may  be  considered  to  be  fourfold : 
to  remove  bacteria,  matter  in  suspension,  matter  in  solution, 
and  color.  Bacteria  might  be  included  under  the  head  of 
"jnatter  in  suspension,"  but  their  importance  and  the  special 
consideration  which  they  receive  make  it  desirable  to  classify 
them  alone.  The  methods  used  for  purification  are  in 
general:  sedimentation;  straining,  or  mechanical  filtration, 
^ith  or  without  the  use  of  coagulants,  commonly  called  the 
American  method;  bacterial  filtration,  in  which  the  organic 
matter  is  oxidized,  commonly  called  the  English  method; 
chemical  purification,  including  softening  of  hard  waters,  and 
removing  iron  in  solution  by  aeration;  and  distillation. 

It  is  only  within  a  very  few  years  that  it  has  been  realized 
that  a  method  of  purification  which  was  adapted  to  one  water 
might  not  be  adapted  to  another.  Thus,  mechanical  filtration 
gives  excellent  results  in  East  Providence,  but  was  a  failure 
at  New  Orleans;  and  sand-filtration,  while  successfully  used 
in  scores  of  European  plants,  has  proved  inapplicable  to  some 
of  our  muddy  streams.  During  1899  to  1901  exhaustive 
investigations  made  at  Louisville,  Pittsburg,  and  Cincinnati, 
and  lesser  ones  at  Quincy,  111.,  and  other  places  have  vastly 
increased  our  knowledge  of  the  possibilities  and  limitation  of 
different  methods  of  purification;   and   the  experiments  con- 

287 


288  WATER-SUPPLY  ENGINEERING. 

ducted  by  the  Massachusetts  State  Board  of  Health  continu- 
ously since  1897  have  been  of  the  greatest  value,  particularly 
in  discovering  the  natural  laws  upon  which  bacterial  action 
depends. 

Art.  76.     Sedimentation. 

Sedimentation  has  already  been  referred  to  (Art.  34)  as  a 
method  of  purification.  It  is,  however,  extremely  slaw  irL_its 
action,  except  in  removing  the  grosser  niatter_s_in  suspensioj). 
The  lower  Ohio  and  Mississippi  rivers  during  floods  contain 
large  quantities  of  clay  particles,  many  of  them  not  more 
than  .00001  inch  diameter,  which  are  present  in  the  water 
for  weeks  at  a  time.  These  settle  very  slowly,  weeks  and 
even  months  being  required  to  wholly  clear  such  water  by 
this  means.  In  time,  however,  all  matters  in  suspension, 
including  all  or  most  of  the  bacceria,  will  be  deposited. 
Sedimentation  requires  that  the  water  be  perfectly  quiet  or 
have  a  very  slow  motion  and  hence  "settling-basins"  are 
necessary  in  which  water  can  be  stored,  while  the  consumption 
is  being  derived  from  duplicate  basins;  or  the  water  is  con- 
tinuously drawn  from  large  basins  so  constructed  that  the 
velocity  of  flow  shall  be  very  low  and  uniform  throughout  the 
basin,  these  being  called  "continuous-flow  basins."  A  clear- 
water  reservoir  should  be  provided  to  receive  the  clarified 
water  from  either  perfect  rest  or  continuous-flow  basins.  At 
Omaha,  Neb.,  five  basins  in  a  series  are  used,  and  the  pro- 
portion of  sediment  deposited  in  each  is  shown  by  the  fact 
that  the  first  two  are  cleaned  once  in  two  weeks,  the  next 
one  once  a  month,  the  next  once  in  six  weeks,  and  the  next, 
which  is  practically  a  clear-water  basin,  once  in  a  year. 
Geo.  W.  Fuller  found,  in  the  Louisville  experiments,  that  in 
quiet  water  75/^  of  the  matter  in  suspension  was  deposited 
in  twenty-four  hours;  but  that  little  more  was  removed 
during  several  days  following.      When  there  was  a  great  deal 


PURIFICATION   OF    WATER.  289 

of  fine  clay  in  the  water  but  50^  was  removed  in  this  time. 
From  the  Cincinnati  experiments  he  concluded  that  "sedi- 
mentation for  more  than  three  days  would  not  be  practicable, 
because:  (i)  the  fine  clay  particles  remaining  after  seventy- 
two  hour's  settlement  subside  very  slowly,  the  percentage  of 
decrease  per  day  being  seldom  more  than  5^  of  the  original 
for  the  fourth  day  and  steadily  decreasing  thereafter;  and 
(2)  the  cost  would  be  excessive."  The  latter  is  evident  when 
we  consider  that,  if  the  method  of  perfect  rest  be  adopted, 
basin-capacity  must  be  provided  equal  to  the  total  consump- 
tion during  the  period  of  rest  plus  a  certain  amount,  say  25^, 
additional  for  sediment,  with  at  least  one  additional  basin 
which  will  be  out  of  service  while  being  emptied  and  filled. 

From  investigations  of  sedimentation  at  St.  Louis  in  1886 
it  was  concluded  that  the  system  of  perfect  rest  was  the  most 
efficient  and  economical;  the  time  allowed,  however,  must 
be  decided  with  reference  to  the  character  of  the  suspended 
matter  in  the  water  to  be  clarified.  From  the  experiments 
on  continuous  flow  it  was  concluded  that  a  flow  of  only  1200 
gals,  per  day  per  square  foot  of  cross-section  of  basin  would 
give  an  effluent  comparable  with  that  from  perfect  rest.  The 
length  of  basin  would  need  to  be  such  that  twenty-four  to 
seventy-two  hours  would  be  consumed  by  each  gallon  of 
water  in  passing  from  the  inlet  to  the  outlet.  Later  investi- 
gations have  only  confirmed  these  conclusions. 

In  some  cases,  where  water  is  ordinarily  clear,  is  occa- 
sionally slightly  muddy,  but  for  infrequent  periods  of  three 
or  four  days  only  is  quite  muddy,  clarification  of  the  last- 
named  water  may  be  avoided  by  providing  storage-reservoirs 
capable  of  supplying  the  consumption  for  this  period,  and 
clarifying  only  the  slightly  muddy  water.  If  the  suspended 
matter  in  this  latter  is  mostly  clay,  however,  the  time 
required  for  complete  clarification  will  be  as  great  as  for  the 
muddiest  water,  and  filtration  would  be  preferable. 


290  WATER-SUPPLY  ENGINEERING. 

The  great  fluctuations  in  the  amount  of  suspended  matter 
carried  by  some  streams  is  illustrated  by  the  Ohio  River, 
which,  during  the  Louisville  experiments,  contained  matter 
varying  from  i  to  531 1  parts  by  weight  per  million  of  water. 

It  might  be  stated  as  a  general  conclusion  that  sedimen- 
tation will  effect  a  considerable  clarification,  the  extent  of 
this  depending  upon  the  fineness  of  the  material  carried;  but 
that  if  much  of  this  is  fine  clay  the  resultant  water  will  hardly 
be  fit  for  domestic  use;  and  that  the  proportion  of  bacteria 
removed  will  be  approximately  the  same  as  that  of  the  fine 
clay.  It  will  be  seen,  however,  that  sedimentation  may  be  a 
valuable  preliminary  to  more  thorough  purification. 

Art.  77.     English  Method  of  Filtration. 

The  English  method  of  filtration  has  been  used  in  more 
water-works  systems,  not  only  in  Europe  but  in  this  country 
also,  than  any  other.  It  is  essentially  a  comparatively  slow 
filtration  through  sand.  (Comparatively  with  reference  to 
the  American  system  of  filtration;  the  sand  filtration  of 
sewage  is  conducted  at  rates  much  lower  than  that  of  water.) 
The  water  is  flooded  upon  a  bed  of  sand  from  2|  to  5  feet 
thick,  and  passes  through  this  at  a  rate  of  i^  to  3  million 
gallons  per  acre  daily.  The  German  government  has  fixed 
2,600,000  gals,  per  acre  per  day  as  the  maximum  rate  of  fil- 
tration permissible,  or  about  four  vertical  inches  per  hour.) 

The  sand  which  forms  the  filtering  material  rests,  in  most 
filters,  upon  a  bed  of  fine  gravel,  and  this  in  turn  upon 
coarser  gravel;  and  the  filtered  water  is  drawn  off  by  under- 
drains.  This  construction  is  necessary,  since  sand  in  contact 
with  the  drains  would  be  washed  into  them,  and  the  material 
placed  around  them  must  also  be  sufificiently  porous  to  permit 
full  access  of  water  to  them.  Hence  the  bottom  layer  is 
often  of  broken  stone,  the  next  of  gravel  one  third  the  size, 


PURIFICATION   OF    WATER.  29 1 

and  successive  layers  of  material  2  to  6  inches  thick  follow, 
each  having  grains,  say,  one  third  the  size  of  those  in  the 
next  lower  layer:  as,  for  instance,  stones,  10  mm.  diameter, 
3.5  mm.  diameter,  1.2  mm.  diameter,  and  .4  mm.  diameter. 
The  top  layer  of  sand  should  not  at  any  time  become  less 
than  12  to  15  inches  thick,  and  is  generally  made  originally 
30  to  40  inches  to  permit  of  removing  clogged  material.  In 
the  Albany,  N.  Y.,  filter-beds,  which  were  put  into  service 
in  August  1899,  and  are  the  largest  in  the  country  and  prob- 
ably represent  the  most  advanced  ideas,  it  was  specified  that 
"  The  lower  7  inches  shall  consist  of  broken  stone  or  gravel, 
which  shall  remain  upon  a  screen  with  a  mesh  of  i  inch,  and 
which  has  but  very  few  stones  over  2  inches  in  diameter. 
Above  this  shall  be  placed  2\  inches  of  broken  stone  or  gravel 
which  has  passed  a  screen  with  a  mesh  of  i  inch,  and  which 
remains  upon  a  screen  with  a  clear  mesh  of  f  inch,  and  above 
this  shall  be  placed  2^  inches  of  broken  stone  or  gravel,  which 
has  passed  a  screen  with  a  mesh  of  f  inch,  and  which  is 
coarser  than  the  ordinary  sand,  and  entirely  free  from  fine 
material.  .  .  .  The  filter-sand  shall  be  clean  river,  beach,  or 
bank  sand,  with  either  sharp  or  rounded  grains.  It  shall  be 
entirely  free  from  clay,  dust,  or  organic  impurities,  and  shall, 
if  necessary,  be  washed  to  remove  such  materials  from  it. 
The  grains  shall,  all  of  them,  be  of  hard  material  which  will 
not  disintegrate,  and  shall  be  of  the  following  diameters:  Not 
more  than  i^,  by  weight,  less  than  0.13  mm.,  nor  more  than 
10^  less  than  0.27  mm.,  at  least  10^,  by  weight,  shall  be 
less  than  0.36  mm.,  and  at  least  70^,  by  weight,  shall  be  less 
than  I  mm.,  and  no  particles  shall  be  more  than  5  mm.  in 
diameter.  The  diameters  of  said  grains  will  be  computed  as 
the  diameters  of  spheres  of  equal  volumes.  The  sand  shall 
not  contain  more  than  2^,  by  weight,  of  lime  and  magnesia 
taken  together  and  calculated  as  carbonates." 

The  size  of  sand-grain  is  generally  expressed  in  terms  of 


292  WATER-SUPPLY  ENGINEERING. 

the  "effective  size"  and  "uniformity  coefficient,"  this 
method  of  classification  originating  with  Allen  Hazen,  the 
designer  of  the  Albany  plant.  The  effective  size  is  defined 
as  "  such  that  10^  of  the  material  is  of  smaller  grains  and 
90^  is  of  larger  grains  than  the  size  given.  The  results 
obtained  at  Lawrence  indicated  that  the  finer  10^  have  as 
much  influence  upon  the  action  of  the  material  in  filtration 
as  the  coarser  90'^."  The  uniformity  coefficient  is  "a  term 
used  to  designate  the  ratio  of  the  size  of  grain  which  has  60^ 
of  the  sample  finer  than  itself  to  the  size  which  has  10^  finer 
than  itself." 

The  fine  top  layer  is  the  filtering  layer,  but  the  most 
effective  agent  in  removing  the  finest  suspended  matters  is  a 
covering  of  slime,  called  by  the  Germans  Schmutzdecke, 
which  forms  upon  the  surface  and  in  the  top  layer  of  the 
sand.  It  is  generally  compact,  membranous,  and  highly 
impervious,  probably  formed  of  a  jelly-like  material  produced 
through  bacterial  agency.  This  covering,  with  the  top  inch 
or  two  of  sand,  does  75  to  85  per  cent  of  the  work  of  strain- 
ing, and  retains  the  finest  matters,  including  clay  and  many 
bacteria. 

A  small  amount  of  matter  in  suspension  is  removed  by 
the  sand  alone,  but  the  principal  change  which  goes  on  here 
— and  which  is  also  carried  on  in  the  Schmutzdecke  above — 
is  the  bacterial  oxidation  of  the  organic  matter,  both  in  sus- 
pension and  solution,  into  the  form  of  nitrites  and  nitrates. 
This  latter  operation  requires  time,  and  for  this  reason  the 
rates  sriven  above  have  been  found  to  be  the  maximum 
desirable.  Another  reason  for  fixing  a  low  rate  is,  that  if  by 
force  a  high  velocity  through  the  Schmutzdecke  is  obtained, 
this  is  apt  to  be  broken ;  the  immediate  cause  of  this  breakage 
being  possibly  a  washing  away  of  part  of  the  supporting  sand 
into  the  under  layer  of  gravel,  owing  to  the  too-high  velocity. 

The  removal  of  bacteria  is  attributed  both  to  the  straining 


PURJFICATIOiY   OF    WATER.  2gi 

action  of  the  gelatinous  covering  and  to  the  removal  of  their 
food-matter  by  its  oxidation. 

It  is  seen  that  the  sand  forms,  not  the  filtering  material 
itself  except  to  a  minor  degree,  but  rather  the  support  and 
habitat  for  the  purifying  agents.  These  are  not  formed 
immediately,  and  no  method  has  yet  been  found  for  supply- 
ing them  artificially;  it  therefore  follows  that  a  new  filter,  or 
one  from  which  the  top  layer  has  been  removed,  can  effect 
the  most  thorough  purification  only  after  these  agents  have 
become  re-established — a  result  which  is  perfected  only  after 
several  days  or  even  weeks  of  use,  although  a  passable  degree 
of  efficiency  is  often  attained  in  three  or  four  days.  In  the 
filter  at  Lawrence,  Mass.,  **  in  the  first  three  days  75^  of  the 
number  of  bacteria  applied  came  through  the  filter.  In  the 
next  three  days  30^  came  through";  and  "during  the  first 
three  weeks'  use  the  number  of  bacteria  in  the  efHuent  rapidly 
decreased  to  2^  of  the  number  applied."  At  Altona, 
Germany,  when  the  filter  has  been  scraped  and  new  sand 
applied,  1880  bacteria  have  been  found  in  the  effluent  after 
one  day,  752  after  two  days,  208  after  three,  156  after  four, 
102  after  five,  and  84  after  six  days,  the  rate  before  scraping 
having  been  42  per  cubic  centimeter. 

As  suspended  matter  collects  on  and  in  the  gelatinous 
covering,  the  pores  of  this  and  the  sand  become  so  choked  as 
to  interfere  with  the  passage  of  water  through  the  filter.  In 
fact,  soon  after  the  filter  is  put  into  service  it  is  found  that 
the  head  of  water  on  the  filter  must  be  increased  to  produce 
the  required  velocity  of  percolation.  The  limit  of  depth  of 
water  permitted  upon  European  filters  is  placed  at  36  to  52 
inches,  or  even  in  some  cases  at  24  inches.  When  the  limit 
is  reached  the  water  on  the  filter  must  be  drawn  off  and 
wasted,  and  the  top  layer  of  compact  material  removed;  this 
layer  amounting  generally  to  from  i^  to  ^  inch,  or  the  least 
that  can  well  be  handled  uniformly.      Water  is  then  turned 


294  WATER-SUPPLY   ENGINEERING. 

slowly  onto  the  bed  —  usually  from  below  —  until  it  is 
thoroughly  filled  and  covered,  when  the  regular  filtration  is 
renewed.  When  the  removal  of  sand  has  reduced  the  thick- 
ness of  that  remaining  to  12,  or  better  15  inches,  new  sand 
must  be  placed  upon  the  filter.  The  lower  the  limit  of  head 
of  water  the  more  often  must  the  filter  be  cleaned;  and  aside 
from  the  expense,  this  is  objectionable  because  of  the  decrease 
in  efficiency  for  some  time  after  cleaning,  and  the  waste  of 
water,  the  quantity  of  which  may  be  already  deficient.  For 
these  reasons  Hazen  recommends  placing  the  limit  of  depth 
of  water  in  the  filter  at  5  or  6  feet,  believing  that  no  harm  to 
the  filter  or  its  top  coating  will  be  occasioned  by  this  if  the 
rate  be  not  increased  above  the  limit.  It  is  probable  that 
this  high  limit  is  most  applicable  to  the  finer  sands,  which 
furnish  a  more  solid  and  continuous  support  for  the  surface 
film ;  but  that  the  pressure  exerted  might  carry  this  down 
into  the  pores  of  a  coarse  sand.  It  would  therefore  seem 
necessary  that  each  filter  determine  for  itself  the  maximum 
head  allowable;  the  head  from  time  to  time,  while  less  than 
this,  being  kept  sufficient  to  maintain  the  rate  of  percolation 
constant. 

The  following  table  gives  the  rates  of  filtration  in  several 
European  plants,  the  majority  being  between  1,600,000  and 
2,700,000  gals,  per  acre  per  day.  As  stated  above,  the  latter 
is  thought  to  be  the  highest  desirable  for  ordinary  conditions. 

Oxygen  is  required  for  the  oxidizing  of  organic  matter  in 
the  water,  and  sufficient  for  this  purpose  is  ordinarily  contained 
in  the  water  itself.  If  this  be  very  impure  and  thus  demand 
much  oxygen,  or  if  it  for  some  reason  contain  little  or  no 
oxygen,  this  is  generally  supplied  by  allowing  the  water  to 
drain  out  of  the  filter  at  short  intervals  of  time,  and  the  pores 
to  become  filled  with  air.  Water  is  then  turned  onto  the 
filter  from  above  and  the  air  in  the  sand  interstices  supplies 
the    necessary    oxygen.      This   method,    called    intermittent 


PURIFICATION   OF    WATER. 


295 


filtration,  is  used  at  Lawrence,  Mass.,  and  is  that  adopted  in 
many  cases  for  sewage  purification.  It  will  probably  be 
required  for  few  river-waters,  however. 

Table  No.  63. 

RATES    OF    FILTRATION    IN    EUROPEAN    CITIES.       (mASON.) 


Place. 


Berlin  (Tegel). . 
Oporto 

Zurich 

Stuttgart 

Altona 

Liverpool 

Chelsea 

East  London. . . 
Grand  Junction 

Lambeth , 

New  River 

Southwark 

West  Middlesex 


U.  S.  Gallons 

per  Acre  per 

Day. 


3.179.880 
13,895,640 
\    7,492,000  to 
\  10,672,000 

2,134,440 
2,613,525 
2,613,525 
2,178,000 

1,655,280 

2,570,000 
2,700,000 
2,570,000 
1,873,000 
1,655,280 


U.  S.  Gallons 

per  Square  Foot 

per  Day. 


319 

172  to  245 

49 
60 

60 
50 
38 
59 
62 

59 
43 

33 


Vertical  Inches 
per  Hour. 


5-0 
21.3 

II.  5  to  16.4 


Since  filter-beds  must  occasionally  be  put  out  of  service 
to  be  cleaned,  and  should  remain  so  until,  after  several  days 
of  slow  filtration  and  wasting  of  the  effluent,  its  efificiency 
again  becomes  normal,  duplicate  beds  are  necessary  for 
furnishing  a  continuous  flow.  If  but  two  beds  be  employed, 
the  capacity  must  be  double  that  required  for  constant  use; 
if  three  be  used,  one  and  a  half  times;  and  if  ten  beds  be 
used,  nine  of  which  can  filter  the  entire  supply  at  any  time 
while  the  tenth  is  being  cleaned,  their  total  area  will  be  but 
11^  greater  than  that  required  for  constant  use.  This,  how- 
ever, assumes  that  each  bed  will  filter  without  cleaning  nine 
times  as  long  as  is  required  for  cleaning  it  and  restoring  its 
efficiency.  If  this  latter  be  taken  as  seven  days,  then  each 
bed  must  require  cleaning  but  five  or  six  times  a  year.  With 
many  filters  this  is  satisfactory,  although  others  may  require 
cleaning  once  a  week  during  certain  seasons.     The  frequency 


296  IV A  TER  SUP  PL  V  ENGINEERING. 

of  scraping,  however,  is  a  function  of  the  quantity  filtered 
and  not  directly  of  time.  In  Europe  the  quantity  filtered 
between  scrapings  ranges  between  25  and  160  million  gallons 
per  acre.  The  time  is  reduced  by  the  sediment  carried  by 
spring  floods,  and  the  algae  occurring  in  summer  and  autumn. 
It  will  in  many  cases  be  found  more  economical,  and  in  most 
will  yield  better  results,  to  remove  50  to  75  per  cent  of  sus- 
pended matter  from  muddy  water  by  sedimentation,  before 
filtering.      By  this  means  the  area  of  filters  required  may  be 

_,  ,,,  ,      quantity  of  water 

reduced  50^  or  more.     The  area  will  be -^r. -. X 

rate  ot  nitration 

(i  -|-  proportion  of  the  area  required  for  continuous  use  which 
is  out  of  service  during  cleaning,  which  may  be  .10  to  .15  or 
even  .50). 

The  rate  of  filtration  which  it  is  desired  to  maintain  is 
obtained  by  regulating  the  head;  and  although  this  will  vary 
with  the  state  of  clogging  due  to  sediment,  its  amount  is 
primarily  dependent  upon  the  resistance  offered  by  the  sand 
and  gravel.  It  is  desirable  to  know  the  amount  of  head  which 
will  be  required,  not  only  as  a  guide  in  the  use  of  the  filter, 
but  to  permit  of  intelligent  designing.  The  frictional  resist- 
ance of  sand  to  water,  when  there  is  no  clogging,  is  found  to 
be  such  that 


V  =  cd 


l\     60     /' 


in  which  v  is  the  velocity  of  water  in  meters  per  day, 
(=  1,071,576  gals,  per  acre  per  day);  c  =  1000  ±  ;  ^  is  the 
effective  size  of  sand  in  millimeters;  /i  is  the  head;  /  is  the 
thickness  of  sand  through  which  the  water  passes;  /  is  the 
degrees  Fahrenheit.  This  law  seems  to  hold  good  only  when 
the  uniformity  coefficient  is  below  5  and  the  effective  size  is 
between  .01  and  3  mm.  The  rates  for  sands  and  gravels  of 
different  sizes  are  given  in  the  following  table: 


P  URIFICA  TION   OF    WA  TER. 


297 


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298  WATER-SUPPLY   ENGINEERING. 

If,  for  instance,  a  flow  of  2^  meters  per  day  (2,679,000 
gals,  per  acre)  be  desired  through  18  inches  of  sand  of  effective 
size  of  0.40  mm.,  6  inches  of  gravel  of  1  mm.,  and  6  inches 
of  3  mm.,  the  total  head  above  the  sand  required  will  be 
.023  -\-  .0025  -\-  .0005  feet  =  .026  feet.  This  head  is  the 
minimum,  and  will  apply  only  for  new  filters,  or  those  just 
cleaned.  As  the  surface  clogs  the  head  will  increase.  With 
any  given  amount  of  clogging,  the  discharge  can  be  increased 
in  any  proportion  by  increasing  the  head  by  the  same  propor- 
tion. In  addition  to  this  head  is  that  necessary  to  cause  the 
flow  of  the  effluent  through  the  drains  into  the  clear-water 
basin. 

The  sand  used  in  European  filters  has  effective  sizes  vary- 
ing between  .17  and  .44  mm.,  the  former  being  used  in 
Holland.  In  the  majority  of  plants,  however,  the  size  is 
from  .31  to  .40  mm.,  and  this  may  be  taken  as  the  range  of 
the  most  practicable  sizes.  Finer  sands  remove  a  larger  per- 
centage of  bacteria,  and  may  be  advisable  for  water  always 
clear;  but  they  will  clog  quickly  with  ordinary  freshet  river- 
water  and  require  too  frequent  scraping.  The  coarse  sand, 
on  the  other  hand,  will  permit  the  sediment  to  penetrate  too 
far  into  the  bed,  and  hence  require  too  thick  a  layer  of  sand 
to  be  removed;  and  their  efficiency  in  removing  bacteria  will 
not  be  so  great.  There  is  also  danger  that  the  rate  of  filtra- 
tion will,  through  carelessness,  be  permitted  to  become  too 
great. 

The  under-drains  should  be  of  such  size,  grade,  and 
frequency  that  they  are  never  full  at  any  point.  They  are 
usually  made  of  sewer-pipe,  with  joints  open  or  wrapped  with 
burlap  or  cheese-cloth,  and  laid  in  slight  depressions  in  the 
bottom  of  the  filter.  The  bottom  of  one  London  filter  is 
entirely  covered  with  3-inch  drain-tile;  while  in  another  the 
drains  are  formed  of  brick  on  edge  with  a  covering  of  brick 


PURIFICATION   OF    WATER. 


299 


laid    flat    and    close    together,    no    mortar    being    used.      The 
latter  method  vvas  used  at  Ilion,  N.  Y. 

Fig.    41    shows    a   section    of    the   Albany  filter-beds,    of 
which   there  are  eight,  each  258  feet  by  121^  feet;    all  being 


}i>iir>i>yt3^^j(_fsK^'f''"""-'-'^^-'y"'""""""""y^ 


Fig.  41. — Section  of  Albany  Filter-beds. 

roofed  over  by  elliptical  groined  arches  of  concrete,  supported 
by  680  brick  piers. 

There  should  be,  connected  with  the  outlet  of  each  filter- 
bed,  a  weir  or  other  appliance  for  measuring  the  discharge,  and 
a  method  of  regulating  this  or  the  supply  to  each  bed.  The 
method  of  regulation  commonly  employed  is  to  alter  the  avail- 
able head  by  raising  the  surface  of  water  at  the  outlet,  rather 
than  to  regulate  at  the  inlet  to  the  filter.  Thus  the  water-surface 
on  the  filter  remains  at  a  constant  height,  while  by  raising  or 
lowering  a  weir  in  the  effluent  chamber  the  head  and  conse- 
quent velocity  are  decreased  or  increased.  An  automatic 
appliance  has  been  used  in  which  the  weir,  being  attached  to 
a  float  in  the  effluent  chamber,  is  kept  at  a  constant  distance 
below  the  surface  of  the  effluent  water,  which  falls  and  thus 
increases  the  head  on  the  filter  as  this  becomes  more  choked. 
The  regulating  appliance  must  be  protected  from  freezing. 

The  walls  and  bottom  of  a  filter  should  be  water-tight  to 
prevent  either  the  loss  of  water  or  the  access  of  impure 
ground-water.  These  have  been  made  of  all  substances  of 
which  reservoirs  have  been  constructed.  In  fact,  a  filter  is 
very    similar    to    a    distributing-reservoir    whose     bottom     is 


300  WATER-SUPPLY  ENGINEERING. 

covered  with  a  system  of  drain-pipes,  and  these  in  turn  with 
gravel  and  sand.  The  best  filter-walls,  however,  are  vertical 
and  formed  of  rough  stone  masonry. 

Where  the  mean  temperature  for  any  month  of  the  year 
falls  below  32°  more  than  occasionally,  or  where  thick  ice 
forms  and  remains  for  a  week  or  more  at  a  time,  filters  should 
be  covered;  since  ice  upon  a  filter  is  almost  sure  to  diminish 
its  efificiency,  and  has  been  known  to  cause  typhoid  fever. 
The  expense  of  removing  ice  from  a  filter,  also,  may  be  con- 
siderable; this  being  $2323  for  the  Lawrence  filter  in  1897 
(2^  acres,  uncovered).  On  an  average  the  cost  of  construct- 
ing covered  filters  in  England  has  been  50^  greater  than  that 
of  uncovered  ones  of  the  same  capacity.  The  expense  of 
operating  open  filters  is  increased  not  only  by  ice,  but  by 
algae  growth,  which  rapidly  clogs  the  filter.  For  roofing  the 
filter,  masonry,  covered  with  earth,  is  preferable  as  excluding 
both  cold  and  heat.  The  form  of  roof  may  be  the  same  as 
for  reservoirs  (see  Art.  74). 

The  first  filter-beds  in  the  United  States  to  be  covered 
with  vaulting  are  thought  to  have  been  built  at  Ashland, 
Wis.,  in  1895-6,  and  cover  an  area  of  about  one  half  acre, 
the  roof  being  of  groined  elliptical  arches  of  about  15I  feet 
span  and  i\  feet  rise.  At  Somerworth,  N.  H.,  another 
filter-plant  with  arched  masonry  roof  was  constructed  in 
1897-8,  the  area  being  148  X  150  feet,  in  two  beds.  At 
Grand  Forks,  N.  Dak.,  in  1894,  a  sand  filter  175  X  102  feet 
was  constructed  with  a  timber  roof,  2-inch  plank  with  tarred 
roofing-felt,  pitch,  and  gravel. 

The  sand  removed  from  a  filter  may  be  used  for  filling  low 
land,  or  may  be  washed  and  used  again,  according  to  the 
relative  value  of  filling  material  and  cost  of  new  sand  as  com- 
pared with  that  of  washing  the  sand.  The  washing  is  done 
in  various  ways;  in  some  plants  a  rotary  washer  like  a  pug 
mill  is  used ;    in   others  the  sand  is  simply  spread  out   and 


PURIFICATION   OF    WATER.  3OI 

washed  with  a  hose.  An  unsuccessful  attempt  was  made  at 
Hudson,  N.  Y.,  to  wash  the  sand  while  on  the  bed  by  forcing 
a  current  of  water  up  through  it.  At  Albany  it  is  intended 
to  wash  the  sand  in  hoppers  through  which  jets  of  water  pass 
upward,  carrying  the  sand  with  it,  which  water,  overflowing 
into  the  drain,  removes  the  dirt.  From  0.5  to  i  per  cent  of 
the  water  filtered  is  generally  required  for  washing  the  sand. 
The  use  of  a  mechanical  agitator  of  some  kind  has  been 
found  to  reduce  the  amount  of  water  which  must  be  used  and 
the  cost. 

The  sand  on  the  top  of  a  scraped  bed  is  partially  clogged, 
and  when  clean  sand  is  placed  on  this  there  is  a  tendency  for 
sediment  to  collect  at  the  surface  of  the  old  sand  where  it 
cannot  be  readily  removed  and  thus  the  entire  filter  to  be 
clogged.  For  this  reason  the  sand  is  renewed  at  as  long 
intervals  as  possible,  and  the  last  scraping  before  renewal  is 
made  unusually  deep.  The  top  of  the  old  and  a  layer  of  the 
new  should  then  be  thoroughly  mixed  before  the  whole  of 
the  new  is  placed.  In  England  it  is  the  general  custom  to 
take  out  the  old  and,  placing  the  new  sand  in  the  bottom, 
replace  the  old  upon  it. 

Filters  are  in  some  cases  placed  so  that  water  will  flow 
upon  them  from  a  river,  reservoir,  or  other  body  of  water  by 
gravity;  but  in  a  majority  of  cases  the  water  is  pumped  onto 
the  filter,  and  the  efifluent  water  pumped  into  the  system. 
The  two  sets  of  pumps  being  generally  in  the  same  building 
and  using  the  same  boiler-plant,  the  efificiency  of  the  plant  is 
not  greatly  decreased  by  the  double  pumping. 

The  efficiency  of  English  sand-filtration  is  thought  to  be 
exceeded  by  that  of  no  other  system.  The  London  filters 
are  reported  as  removing  an  average  during  three  years  of 
97.6^  of  the  bacteria.  The  Altona,  Germany,  filters  during 
February  1 893  removed  99.69^  of  the  bacteria.* 

It    is    apparent    that    if    very    muddy    water   were    to    be 

*  Sec  also  Appendix  C 


302  WATER-SUPPLY  ENGINEERING. 

handled  an  English  filter  would  quickly  become  clogged,  and 
it  might  be  necessary  to  have  two  or  three  times  the  service 
area  to  permit  of  frequent  cleaning.  In  fact  the  Cincinnati 
tests  appeared  to  show  that  at  times  the  Ohio  River  water 
could  not  be  rendered  satisfactory  in  appearance  and  character 
by  these  filters  alone.  "  So  far  as  the  information  goes  it 
appears  that  an  average  of  125  parts  per  million  is  a  con- 
servative estimate  of  the  amount  of  suspended  matters  in  the 
unsubsided  river-water,  which  could  be  regularly  and  fairly 
satisfactorily  handled  by  English  filters";  and  this  amount 
was  exceeded  during  230  days  in  1898.  While  they  can 
handle  this  amount  of  silt  in  untreated  water,  experience 
seems  to  show  that  in  subsided  water  they  can  remove  the 
suspended  clay  in  amounts  ranging  only  as  high  as  from  30 
to  70  parts,  and  averaging  about  50  parts  per  million.  This 
is  because  the  total  matter  in  suspension  in  the  subsided 
water  is  fine  clay,  while  in  raw  water  about  one  half  of  the 
suspended  matter  is  in  larger  particles.  It  was  found  at 
Cincinnati  that  if  the  water  be  first  clarified  by  sedimentation 
for  two  or  three  days  and  75^  of  the  suspended  matter 
removed,  English  filters  would  have  worked  satisfactorily  but 
231  days  of  the  year,  or  64^  of  the  time.  For  such  rivers, 
therefore,  these  filters  are  not  applicable  as  now  used.  But 
it  must  be  remembered  that  the  Ohio  at  Cincinnati  is  excep- 
tionally muddy  at  certain  seasons,  and  these  objections  will 
not  be  found  existing  to  such  an  extent  in  a  majority  of 
cases. 

If  a  small  quantity  of  alum,  or  sulphate  of  alumina,  be 
added  to  a  water,  the  alum  is  decomposed  into  its  component 
sulphuric  acid  and  alumina,  and  the  sulphuric  acid  combines 
with  lime,  magnesia,  or  some  other  base  in  the  water;  the 
alum  forms  a  hydrate  of  alumina,  which  settles  through  the 
water  in  a  gelatinous  mass,  entangling  with  it  any  matters  in 


PURIFICATION   OF    WATER.  303 

suspension,  and  also  causing  chemical  changes  not  well  under- 
stood by  which  dissolved  organic  matter  and  color  are 
removed  from  the  water.  This  method  is  used  in  a  large 
number  of  sewage-purification  works  under  the  name  of 
chemical  precipitation.  It  has  been  used  in  a  few  cases  as  a 
preliminary  to  treatment  by  English  filters.  It  was  found  in 
the  Louisville  experiments  that  a  part  of  the  alum  was  not 
available  as  a  clarifier,  but  was  absorbed  by  the  suspended 
matter.  The  exact  amount  so  lost  under  different  conditions 
was  not  accurately  learned,  but  with  400  parts  per  million  of 
suspended  matter  about  one  half  grain  of  sulphate  of  alumina 
per  gallon  of  water  was  so  absorbed.  It  was  also  found  that, 
by  first  permitting  the  larger  particles  to  settle  out  by  plain 
sedimentation  for  a  day,  not  only  was  the  amount  of  coagu- 
lant necessary  for  use  reduced,  but  the  results  obtained  were 
uniformly  better.  In  some  instances  this  threefold  process 
may  give  the  best  results,  sedimentation  removing  the  larger 
particles,  precipitation  by  the  coagulant  much  of  the  finer 
matter  in  suspension,  and  finally  filtration  through  sand 
removing  most  of  the  remaining  matters  in  suspension,  in- 
cluding bacteria,  and  much  of  the  organic  matter  in  solution. 
In  many  cases  an  English  filter  alone  would  work  satisfactorily 
for  three  fourths  of  the  time;  and  for  the  remaining  season 
of  muddy  water,  if  preceded  by  sedimentation  and  precipita- 
tion;  the  use  and  expense  of  alum  thus  extending  over  but 
one  fourth  of  the  year. 

The  main  objection  to  the  use  of  alum  is,  that  if  there  be 
an  insufficient  amount  of  lime  or  other  carbonate  in  the  water 
to  serve  as  a  base,  the  alum  is  not  all  dissolved  and  a  part  of 
the  sulphuric  acid  remains  free;  but  this  can  be  corrected  by 
the  addition  of  soda-ash  or  lime  to  the  water.  If  ordinary 
care  be  used,  the  amounts  of  acid  or  of  alum  in  the  effluent 
will  be  so  insignificant  as  to  be  harmless,  one  part  of  alum  in 
100,000  to    10,000  of  water  being  the  ordinary  range  of  use; 


304  WATER-SUPPLY  ENGINEERING. 

or  ^  to  5  grains  per  gallon.  By  each  grain  of  sulphate  of 
alumina  approximately  half  a  grain  of  carbonate  of  lime  is 
converted  into  sulphate  of  lime,  0.2  grain  of  carbonic  acid 
being  liberated,  and  these  pass  off  with  the  filtered  water. 
Perhaps  the  greatest  objection  to  the  sulphate  of  lime  is  its 
tendency  to  form  a  hard  scale  in  boilers;  while  the  carbonic 
acid  facilitates  the  corrosion  of  unprotected  iron. 

Art.  78.     Mechanical  Filters. 

The  descent  through  water  of  the  hydrate  of  alumina  and 
the  matters  coagulated  by  it  is  extremely  slow,  and  to  hasten 
the  process  of  purification  the  plan  has  been  adopted  of  filter- 
ing out  the  coagulated  matter,  and  also  passing  the  water 
through  it  and  causing  it  to  act  as  a  filter.  Some  support 
for  the  coagulant  must  be  provided,  and  a  bed  of  sand  is  used 
for  this  purpose,  the  coagulant  forming  a  layer  upon  and  in 
the  top  of  this.  This  process  is  similar  to  English  filtration, 
the  alumina  hydrate  taking  the  place  of  the  naturally  formed 
Schmutzdecke.  By  increasing  the  amount  of  alum  the 
coagulation  and  also  the  thickness  of  this  coating  and  its 
filtering  power  can  be  increased;  and  it  has  been  found  possi- 
ble to  filter  water  at  fifty  to  one  hundred  times  the  rate  con- 
sidered possible  for  English  filters,  or  from  50  to  300  million 
gallons  per  acre  daily.  Since  the  amount  of  suspended 
matter  removed  is  proportional  to  the  amount  of  water  puri- 
fied, it  follows  that  the  clogging  of  such  filters  must  be  fifty 
to  one  hundred  times  as  rapid  as  in  the  case  of  English  filters. 
Moreover,  the  high  velocity  carries  the  sediment  further  into 
the  sand-bed,  and  after  running  for  a  comparatively  short 
time  it  will  be  carried  entirely  through  into  the  effluent.  It 
is  therefore  necessary  not  only  to  clean  the  filter  at  short 
intervals,  but  the  entire  bed  of  sand  must  be  cleaned  each 
time  and  not  the  top  layer  only.     Practically  the  only  material 


PURIFICATION   OF    WATER.  305 

difference  between  the  various  mechanical  filters — as  these 
hiijh-rate  filters  are  called — are  the  methods  of  cleanincr  the 
sand  and  of  applying  the  coagulant.  Isaiah  S.  Hyatt,  on 
Feb.  19,  1884,  patented  the  process  of  purification  by  the 
use  of  alum  or  other  coagulants  which  would  "obviate  the 
necessity  of  employing  settling-basins."  After  nine  or  more 
years  of  litigation  by  various  companies  concerning  the 
validity  and  scope  of  this  patent  the  most  of  these  have  now 
(August  1899)  combined  in  the  New  York-Jewell  Filter 
Company.  The  general  design  of  American  filters  as  now 
manufactured  is  shown  in  Fig.  42.  The  water,  the  coagulant 
having  first  been  added,  is  ordinarily  admitted  at  the  top  and 
forced  by  gravity  or  pump  pressure  through  the  filtering-coke 
and  sand  and  into  the  outlet-pipe.  When  the  filtering 
material  is  to  be  cleaned,  water,  either  purified  or  raw 
(preferably  the  former),  is  admitted  through  the  outlet-pipe 
and  forced  up  through  the  sand,  agitating  this  thoroughly 
and  washing  out  the  collected  sediment  through  a  waste-pipe. 
This  washing  is  continued  until  the  effluent  runs  clear.  In 
some  filters  the  sand  is  agitated  by  revolving  arms  while  the 
washing  continues.  When  the  filtering  material  is  clean, 
water  is  again  admitted  from  the  top  and  filtering  renewed. 
The  head  necessary  to  force  water  through  the  filter  at  the 
desired  speed  varies  from  6  inches  to  6  feet,  depending  upon 
the  rate,  the  fineness  of  the  sand  used,  and  the  state  of  the 
filter  as  to  clogging.  This  head  is  obtained  either  by  gravity, 
or  by  pumping  into  closed  cylinders  which  contain  the  filter- 
ing material.  The  latter  plan  is  more  frequently  adopted, 
and  is  that  shown  in  the  illustration,  page  306. 

Tests  of  the  efftciency,   best  methods  of  operating,   and 
cost   of  mechanical  filtration  have  been  made  at  Providence,  • 
R.  I.,  in  1893,  at  Louisville,  Ky.,  in  1895-6.  at  Lorain,  O., 
in    1897,   at   Pittsburg,    Pa.,   and  Cincinnati  in    1898,  and  at 
East  Providence,  R,  I.,  in  1899.     Allen  Hazen  was  chemist 


3o6 


WA  TER-SUPPL  Y  ENGINEERING, 


and  bacteriologist  for  the  Lorain  and  Pittsburg  tests,  Geo.  W. 
Fuller  for  those  at  Cincinnati  and  Louisville,  and  Edmund  R. 
Weston  for  those  at  Providence  and  East  Providence.      From 


NTasE«£a 


Fig.  42. — Automatic  Pressure-filter. 


these  a  large  amount  of  valuable  information  was  obtained, 
the  more  important  points  of  which  are  summarized  below. 

In  the  Providence  test  92  to  99  per  cent  of  the  bacteria 
were  removed  when  the  filtering  was  at  a  rate  of  128  million 
gallons  per  acre  daily;  in  the  East  Providence  test  96.56  to 
100  per  cent  were  removed,  the  average  for  3^  months  being 


PURIFICATION  OF   WATER.  307 

99.24^,  when  filtering  at  the  rate  of  125  million  gallons  per 
acre  daily  and  using  one  grain  of  alum  per  gallon  as  a 
coagulant. 

In  the  Lorain  test  of  five  weeks'  duration  the  bacteria 
removed  when  using  2.45  grains  of  alum  per  gallon  were  from 
97.5  to  98.9  per  cent  of  those  in  the  raw  water;  with  1.07 
grains  of  alum  per  gallon  the  bacterial  efficiency  fell  to  90.9^; 
and  with  0.89  grain  the  efficiency  was  but  86.3^;  the  rate 
of  filtration  being  from  6"]  to  80  million  gallons  per  acre  daily. 

In  the  Pittsburg  test  the  bacterial  efificiency  varied  from 
93.23'^  when  0.56  grains  of  alum  per  gallon  were  used  and 
the  rate  of  filtration  was  98  million  gallons,  to  98.96^  when 
using  1.36  grains  of  alum  per  gallon  and  filtering  at  the  rate 
of  103  million  gallons  per  acre  daily;  the  average  being 
97.85^  when  using  1. 18  grains  of  alum  per  gallon  and  filtering 
at  the  rate  of  109  million  gallons. 

In  the  Louisville  experiments  filtration  at  the  rate  of  33 
to  155  million  gallons  per  acre  daily,  and  the  use  of  \  to  12 
grains  of  alum,  gave  widely  varying  results,  there  being  at 
times  200  or  even  300  bacteria  per  cubic  centimeter  in  the 
efifluent;  but  it  was  concluded  from  final  tests  that  a  bacterial 
efficiency  of  99^  was  obtainable  with  careful  management; 
and  this  opinion  has  been  confirmed  by  the  Cincinnati  tests. 

The  clarification  of  the  water  in  the  Providence  experi- 
ments averaged  80^,  in  the  East  Providence  experiments 
83^^.  In  the  Pittsburg  experiments  the  average  reduction  in 
color  was  88^^,  and  in  turbidity  98^,^.  At  Lorain  the  water 
had  little  color,  turbidity,  or  sediment,  all  of  which  were 
removed  by  filtration. 

In  the  East  Providence  experiments  the  "  total  solids'* 
were  reduced  6^;  free  ammonia,  29^;  albuminoid  ammonia, 
63^;  and  the  hardness  was  increased  20,'^. 

At  Pittsburg  the  solids  were  reduced  37i^;  free  ammonia, 
6.6^;  albuminoid  ammonia,  48^;  hardness,  5^^. 


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PURIFICATION   OF    WATER. 


309 


Tahlk   No.   65. — [Continued.) 
Chemical   and    Physical    Results. 


East 

LOKA 

IN,    0. 

Prov- 

IDHNCE, 

R.  I. 

Pittsburg,  Pa. 

Reduc- 

. 

Sand  Filters. 

tion  by 

a 

s 

Lake- 
water. 

Ef- 
fluent. 

Filtra- 
tion, 
•  Per 

> 

11 

I-  3 

No.  I. 

No.  4. 

Cent. 

a! 

0 

!S 

tn 

0.05 
Distinct 

83 

0.03 
0.004 

0  03 
0.002 

0.24 
0.14 

0.07 

O.OIO 

0.07 
0.012 

Turbidity 

.None 

0.20 

Free  ammonia 

0.0015 

0.0014 

29 

0.0020 

0.0022 

0.0019 

0.0018 

0.0020 

0.0018 

0.0018 

Alljuminoid  ammo- 

ma   

0.0146 

0.0076 

63 

O.OIOI 

O.OIOO 

0.0047 

0.0044 

0.0092 

0.0054 

0 . 0053 

Nitrogen  as  nitrates 

0.0170 

0.0170 

0.0568 

0.0611 

0.0512 

0.0491 

0.0581 

0.0642 

0.0549 

'■        "   nitrites 

0.000^ 

Trace 

0.0000 

0.0000 

0.0000 

0.0000 

0.0000 

0.0000 

0.0000 

Total  solids     

27.3000 

23.0000 

6 

15.4 

15.0 

9-3 

9-S 

II. 9 

10.8 

10.6 

Volatile  solids..   ... 

1 2 . 0000 

8.0000 

Chlorine 

0.5800 

C.6000 

I 

1.87 

1-73 

1.71 

1.71 

1.80 

1.84 

1.77 

O.Wfjen  consumed.. 

0. J300 

0 . 1 300 

Temporary  hardness 

9.4000 

7.4000 

Permanent 

1 . DOOO 

3.0000 

Total  hardness.   . . 

1 1 . 0000 

10.4000 

—  20 

3.21 

3-3' 

2.92 

3-03 

3  27 

4-31 

4-33 

2.44 

2.56 

1.61 

1.72 

2.49 

3-53 

3-56 

The  results  of  the  Pittsburg,  Lorain,  and  East  Providenc 
experiments  are  given  more  in  detail  in  Table  No.  65. 

Concerning  the  amount  of  sulphate  of  alumina  required, 
Hazen  concludes  from  his  Pittsburg  experiments  that  the 
amounts  given  in  the  table  on  page  310  will  be  neces.sary  for 
different  percentages  of  bacterial  efificiency  and  of  turbidity. 

Fuller,  from  his  Cincinnati  experiments,  concludes  that 
the  desired  purification  can  be  obtained  at  that  place  by  pre- 
cipitation for  48  hours,  followed  by  treatment  with  1.6  grains 
per  gallon  of  alum,  filtration  being  at  the  rate  of  125  million 
gallons  per  acre.  He  also  fixes  10  feet  as  the  maximum  head 
on  the  filter  desirable;  and  a  depth  of  sand  of  30  inches, 
having  an  effective  size  of  .35  mm. 

The  amount  of  water  required  for  washing  the  filter  both 
Hazen  and  Fuller  find  to  be  about  5^  of  that  filtered;  and 
Hazen  finds  that,  although  the  efficiency  of  the  filter  is 
reduced  for  about  20  minutes  after  each  washing,  the  effect 
upon  the  filtrate  is  insignificant  and  this  water  need  not  be 
wasted. 


3IO 


WATER-SUPPLY  ENGINEERING. 


SULPHATE    OF    ALUMINA    REQUIRED    FOR    DIFFERENT    EFFICIENCIES 
AND    TURBIDITIES. 


Bacterial 

Efficiency, 

Per  Cent 

Removed. 


Required  Amount  of  Sulphate  of  Alumina,  Grains  per  Gallon. 


Least  Turbid 
Waters. 


Preceding  Amount 
sufficient  for  Tur- 
bidities up  to  ♦ 


Extra  Quantity  for 

Higher  Turbidities 

throughout  the 

Year. 


Average 
Quantity 
throughout 
the  Year. 


WARREN    FILTER. 

(Effective  size  of  sand,  0.63  mm.;  uniformity  coefficient,  i.i.) 


95 

0.37 

0.03 

0.33 

0.70 

96 

0.44 

0.06 

0.28 

0.72 

97 

0.56 

O.II 

0.22 

0.7S 

98 

0.84 

0.22 

0.14 

0.98 

98.5 

1. 12 

0.34 

O.IO 

1.22 

99.0 

1.60 

0.53 

0.06 

1.66 

JEWELL    FILTER. 

(Effective  size  of  sand,  0.46  mm.;  uniformity  coefficient,  1.4.) 


95 

0.42 

0.07 

0.18 

0.60 

96 

0.49 

0.12 

0.15 

0.64 

97 

0.65 

0.21 

0. 10 

0.75 

98 

0.96 

0-39 

0.06 

1.02 

98-5 

1.48 

0.70 

0.02 

1.50 

*  The  coefficient  of  turbidity  is  the  reciprocal  of  the  depth  in  inches  beneath  the  surface  of 
the  water  at  wrhich  a  platinum  wire  .04  in.  thick  is  just  ready  to  disappear  from  view.  See 
page  19. 

It  was  found  at  Pittsburg  that  if  the  filtering  material  be 
occasionally  washed  by  placing  upon  it  i  lb.  of  soda  ash  per 
square  foot  of  surface  and  boiling  the  whole  by  applying 
steam  through  the  bottom  pipe,  the  filter  is  given  new  life, 
and  the  length  between  washings  possible  and  quantitative 
efificiency  are  both  increased. 

The  largest  mechanical-filter  plant  is  that  at  Little  Falls, 
N.  J. — thirty-two  rectangular  concrete  filter-tanks  with  a  ca- 
pacity of  32,000,000  gals,  per  day,  or  121  million  gallons  per 
acre  per  day. 

Art.  79.    Other  Filtering  Methods. 
A  few  water-supply  systems  have  combined   intakes  and 
filtration-plants,  one  such  arrangement  being  that  of  "filter- 
galleries  "   described   in   Art.  42 ;  while   another,    used   mostly 


PUKIFICA  TION    OF    IV A  TER.  3  I  I 

in  the  Allegheny  River,  consists  of  a  crib  placed  in  a  river  or 
lake  and  covered  with  sand.  A  section  of  such  a  filter-crib 
used  at  Kensington,  Pa.,  is  shown  in  Fig.  43.     This  is  essen- 


FiG.  43. — Filter-crib;    Kensington,  Pa. 

tially  a  sand  filter,  which  is  used  at  the  rate  of  16  million  gal- 
lons per  acre  per  day  in  the  Kensington  plant.  No  coagulant 
is  used,  of  course,  nor  is  its  use  possible,  and  it  is  doubtful  if 
the  Schmutzdecke  forms  on  such  a  filter  to  any  extent.  A 
crib  through  which  the  Pennsylvania  Water  Company  pumps 
Allegheny  River  water  was  found  in  1897  to  reduce  the 
number  of  bacteria  from  an  average  of  3542  to  one  of  266  per 
cubic  centimeter,  and  to  generally  decrease  the  albuminoid 
ammonia  and  nitrates;  while  the  total  solids  were  decreased 
from  a  maximum  of  448  parts  per  million  to  140  parts  in  the 
corresponding  effluent.  The  main  object,  however,  for  which 
these  cribs  are  used  has  been  clarification  rather  than  purifica- 
tion, and  for  this  they  seem  fairly  well  adapted.  Arrange- 
ment is  usually  made  for  pumping  water  into  the  crib  and 
thus  out  through  the  sand  for  the  purpose  of  cleansing  it  of 
sediment. 

A  method  of  mechanical  filtration  which  was  adopted 
about  seven  years  ago  at  Worms,  Germany,  and  has  been 
recently  advocated  in  this  country,  is  by  the  use  of  hollow 
slabs  or  flat  boxes  of  artificial  porous  sandstone.  This  stone 
is  formed  of  a  mixture  of  clean  river-sand  and  silicate  of  lime 
and  soda,  which  is  baked  in  ovens.      These  slabs,  which  are 


3  1 2  WA  7-EE-S  UP  PL  Y  ENGINEERING. 

3^  feet  square  and  4  inches  thick,  rest  on  end,  in  the 
unfiltered  water,  which  percolates  through  to  their  hollow 
interiors,  these  being  connected  with  a  clear-water  pipe 
beneath  them,  into  which  pipe  the  water  passes.  The  slabs 
are  treated  like  English  filters,  and  the  same  film  forms  upon 
their  surfaces,  the  only  advantage  claimed  being  economy  of 
space.  At  Worms  the  plates  were  placed  in  a  covered  filter 
which  had  previously  been  used  for  English  filtration,  and 
the  quantitative  efficiency  of  this  area  was  increased  eightfold. 
The  filter-plates  are  cleaned  by  reversing  the  current  or  by 
scrubbing.  Experiments  made  on  these  at  Pittsburg  "  did 
not  indicate  that  the  requisite  amount  of  pure  water  could  be 
secured  under  all  conditions  "  ;  and  the  first  cost  and  operat- 
ing expenses  were  considered  excessive.  The  plates  broke 
under  a  wash-water  pressure  of  20  feet. 

About  1865  a  similar  plan  for  filtering  through  slabs  of 
charcoal  was  devised,  but  found  impracticable. 

The  removal  of  iron  from  ground-water  has  been  effected 
in  several  ways.  At  Atlantic  Highlands,  Asbury  Park,  and 
Keyport,  N.  J.,  Reading,  Mass.,  and  other  places  mechanical 
filters  are  used,  preceded  by  aeration  by  which  the  iron  is 
oxidised  into  an  insoluble  compound.  At  Keyport  and 
Reading  lime  is  used  as  a  coagulant,  but  no  chemical  is  used 
at  the  other  places  named.  The  result  seems  satisfactory, 
although  8  to  10  per  cent  of  the  filtered  water  was  required 
for  washing  the  filters  at  Atlantic  Highlands  and  Asbury  Park 
in  1896. 

Experiments  with  coke  breeze  (screenings  from  com- 
mercial coke)  in  1896  at  Provincetown,  Mass.,  showed  an 
efificiency  of  93  to  98  per  cent  of  iron  removed  when  the 
water  was  passed  through  the  breeze,  arranged  as  a  filter  3^ 
feet  deep,  at  a  rate  of  one  million  gallons  per  acre  daily. 
Aeration    and    filtration    of    the    same    water    through    sand 


PURIFICATION   OF    WATER.  313 

removed  but  20^  of  the  iron,  of  which  the  water  contained 
0.495  parts  per  100,000. 

The  Anderson  process  has  been  used  in  a  number  of 
places  in  Europe  and  in  this  country.  It  consists  essentially 
in  bringing  the  water  to  be  purified  in  contact  for  three  or 
four  minutes  with  iron,  preferably  cast-iron  borings  or  turn- 
ings, then  aerating,  settling,  and  filtering  it.  Contact  with 
the  iron  is  secured  by  passing  the  water  through  revolving 
cylinders  containing  particles  of  iron,  the  cylinders  having 
shelves  or  ledges  so  arranged  as  to  continually  shower  the  iron 
through  the  water.  The  water  is  aerated  just  before  entering 
the  cylinders.  Before  leaving  them  it  is  said  to  be  charged 
with  a  proto-salt  of  iron,  which,  by  a  second  aeration,  is 
changed  into  an  insoluble  ferric  oxide.  The  water  is  then 
filtered.  The  ferric  oxide  in  this  process  acts  as  a  coagulant, 
but  is  not  thought  to  be  so  effective  as  sulphate  of  alumina. 
From  0.1  to  0.2  grain  of  iron  per  gallon  are  claimed  by  the 
Anderson  Company  to  be  taken  up  by  the  water. 

A  modification  of  this  method  has  been  used  at  Wilming- 
ton, Del.,  since  the  latter  part  of  1894,  in  which  bundles  of 
revolving  iron  rods  in  a  channel  traversed  by  the  water  take 
the  place  of  the  Anderson  cylinder,  and  the  filtration  is 
upward  through  sand-beds.  As  the  iron  yielded  by  the  rods 
is  less  than  .01  grain  per  gallon  it  is  evident  that  this  has 
little  effect  upon  the  result,  which  is  due  to  aeration  and 
sand-filtration  alone. 

So-called  electrical  purification  of  water  is  really  but  an 
electrolytical  production  of  cogulant  in  the  water  to  be 
treated ;  but  the  cost  by  any  method  yet  adopted  seems  to 
be  excessive,  and  the  regular  formation  of  coagulant  not 
under  control.  On  the  other  hand,  aluminum  and  iron 
hydrates  do  not  decrease  the  hardness,  corroding  or  encrust- 


314  WATER-SUPPLY  ENGINEERING. 

ing  qualities  of  the  water,  as  does  sulphate  of  alumina;  and 
it  is  possible  that  the  electrical  production  of  coagulents  will 
yet  be  made  a  practical  and  commercial  success. 

The  softening  of  hard  water  (see  Art.  6)  is  a  very  impor- 
tant factor  in  preparing  it  for  use  in  the  laundry  and  for 
boilers,  as  well  as  in  rendering  it  more  potable.  Temporary 
hardness  can  be  removed  (i)  by  boiling,  when  it  forms  a 
compact  sediment;  (2)  by  adding  carbonate  of  soda,  which 
combines  with  the  bicarbonate  of  lime  in  the  water,  and 
bicarbonate  of  soda  and  carbonate  of  lime  result.  The 
former  remains  in  solution  but  does  not  render  the  water 
hard,  and  the  latter  is  precipitated  as  a  fine  powder.  (3)  By 
lime-water  (a  solution  of  freshly  burned  lime),  \vhich  unites 
with  a  part  of  the  carbonic  acid  in  the  carbonates  of  lime  or 
magnesia,  and  reduces  these  and  itself  to  insoluble  mono- 
carbonates  which  form  a  fine  precipitate;  which  process  is  the 
least  expensive.  Permanent  hardness  can  be  removed  by 
adding  carbonate  of  soda,  which,  uniting  with  the  sulphate 
of  lime  or  of  magnesia,  forms  an  insoluble  carbonate  of  these 
bases,  together  with  sulphate  of  soda,  which  remains  in  solu- 
tion but  does  not  harden  the  water.  When  water  is  both 
permanently  and  temporarily  hard,  as  is  usually  the  case,  a 
mixture  of  lime  and  carbonate  of  soda  generally  gives  the 
best  results. 

At  Southampton,  Eng.,  of  25.7  parts  of  carbonate  of  lime 
in  100,000  parts  of  water,  18.7  parts  are  removed  by  adding 
22  parts,  by  weight,  of  lime,  which  is  first  slaked  and  mixed 
with  water  to  form  a  creamy  fluid.  After  receiving  the  lime- 
water  the  water  stands  for  an  hour,  and  the  insoluble  lime  is 
then  filtered  out;  this  being  called  the  Clark  process.  The 
filtering  has  been  rendered  unnecessary  by  a  recent  improve- 
ment of  Clark's  method,  by  which  the  precipitate  of  a 
previously  softened  water,  which  has  become  aggregated  into 


PURIFICATION  OF    WATER.  31$ 

coarse  flakes,  is  mixed  with  that  just  softened,  and  in  setthng 
carries  down  the  fine  particles  of  fresh  precipitate  much  more 
rapidly  than  they  would  otherwise  settle.  Thus  rapid  pre- 
cipitation takes  the  place  of  filtration  at  less  expense  and  in 
less  time.  This  modification  of  the  Clark  process,  with  other 
minor  changes  in  application  of  the  chemical  and  in  the 
precipitation-tanks,  is  known  as  the  Archbutt-Deeley  process. 
(See  Engineer i7ig  Ncivs,  vol.  XL.  page  403.) 

In  any  process  where  cliemicals  are  used  it  is  necessary 
that  some  arrangement  be  made  for  admitting  at  all  times  the 
proper  amount  of  chemical,  which  will  vary  with  both  the 
quantity  and  character  of  the  water.  Many  methods  of 
accomplishing  this  are  in  use,  but  few  are  satisfactory.  In 
using  lime,  alum,  and  other  solid  chemicals,  these  are  first 
mixed  with  or  dissolved  in  a  small  amount  of  water,  and  this 
concentrated  solution  is  then  admitted  to  the  water  to  be 
treated.  If  the  character  of  the  water  is  constant,  the  solu- 
tion may  be  kept  at  a  uniform  strength,  and  the  amount  of 
this  proportioned  to  the  amount  of  water  treated,  by  auto- 
matic connection  with  the  pump  delivering  it  or  in  some 
other  way.  If  the  quality  of  water  vary,  either  the  strength 
or  quantity  of  the  chemical  solution  may  be  correspondingly 
changed;  the  former  being  the  plan  generally  adopted  as  the 
most  reliable  and  least  troublesome. 

Distillation  as  a  method  of  purification  is  not  adapted  to 
city  supplies,  because  of  both  the  great  cost  and  the  peculiar 
flat  taste  of  distilled  water  which  renders  it  objectionable  to 
most  persons.  The  United  States  Navy  is  probably  the  most 
extensive  user  of  distilled  water,  this  being  the  only  supply 
on  practically  all  its  vessels;  but  it  is  there  an  alternative  of 
stored  water,  which  it  would  often  be  necessary  to  obtain 
from  sources  of  doubtful  purity. 


3l6  WATER-SUPPLY   ENGINEERING. 

Household  filters  are  manufactured  of  many  designs,  some 
using  chemicals,  but  most  of  them  straining  the  water  only. 
From  what  has  been  said  it  is  evident  that  a  chemical  filter 
in  particular  needs  careful  attention  to  be  efficient,  and  this 
it  seldom  receives  in  a  household.  Of  the  straining-filters 
the  Pasteur  is  one  of  the  best,  porcelain  being  the  filtering 
medium.  But  through  even  this  bacteria  have  been  known 
to  pass,  probably  by  a  process  of  growth  rather  than  by 
passing  bodily  through  it.  Hence  these  filters  should  be 
cleaned  and  boiled  at  least  once  a  week.  Many  other  filters 
become  foul  in  much  less  time,  and  after  use  for  six  to  twelve 
hours  render  the  water  passing  through  them  vastly  more 
polluted  than  if  not  "  filtered."  This  result  might  be  antici- 
pated from  the  high  rates  at  which  they  pass  the  water.  It 
can  be  safely  said  that  any  filter  which  delivers  water  directly 
from  the  faucet,  rather  than  filtering  continuously  and  storing 
the  filtrate,  is  much  worse  than  no  filter  at  all;  and  that,  for 
a  household  of  six,  a  continuously  flowing  filter  without 
chemicals  should  have  a  surface  area  of  at  least  lo  square 
feet,  and  with  chemicals  of  28  square  inches. 

Art.  so.     Summary. 

For  softening  water  the  Clark  process  forms  the  basis  of 
all  satisfactory  methods  in  use. 

For  removing  iron  from  water  the  method  of  aeration,  and 
removing  the  resulting  insoluble  ferric  oxide  by  filtration,  or 
sedimentation,  or  both,  is  practicable  and  satisfactory  if  the 
details  of  the  operation  be  properly  conducted. 

For  removing  clay  and  other  inorganic  matters,  sedimen- 
tation followed  by  filtration  gives  good  results,  and  when 
there  is  little  matter  to  be  removed  the  sedimentation  may 
be   omitted.      For  this   purpose    mechanical    filters    using    a 


PURIFICATION   OF    WATER.  317 

coagulant  are  better  than  slow  sand  (English)  filtcis;  but  not 
so  good  as  these  if  no  coagulant  be  used. 

For  removing  bacteria  and  other  organic  matter  English 
filters  give  the  best  results;  although  mechanical  filters  with 
coagulation  have  given  an  efficiency  only  ^  to  2  per  cent 
less.  But  the  possibility  of  occasional  serious  lapses  in  full 
efficiency  is  greater  with  mechanical  than  with  English  filters. 

When  it  is  desired  to  remove  two  or  more  of  the  above 
classes  of  impurities,  the  choice  of  method  requires  more 
careful  consideration.  If  the  suspended  matter  never  exceeds 
100  to  125  parts  per  million,  and  seldom  75  parts,  English 
filters  are  probably  to  be  preferred  for  removing  this  and 
organic  matter;  but  if  more  than  this  be  present,  sedimenta- 
tion, followed  in  more  extreme  cases  by  coagulation  and  a 
short  rest,  are  necessary  before  filtering  with  the  English 
filter;  or  a  mechanical  filter  may  be  used  with  coagulants. 
Which  of  these  is  preferable  will  depend  on  various  local  con- 
ditions, and  characteristics  of  the  water  in  question. 

If  the  water  contains  very  much  fine  clay,  mechanical 
filtration  preceded  by  sedimentation  is  probably  the  best 
solution. 

If  iron  is  to  be  removed  in  addition  to  suspended  and 
organic  matter,  aeration  may  precede  the  other  processes  and 
the  iron  thus  become  part  of  the  suspended  matter  to  be 
removed. 

Softening  is  generally  best  accomplished  after  other 
purification  has  been  completed. 

The  following  table  gives  some  data  concerning  the  filtra- 
tion of  water-supplies  in  the  United  States.  It  was  compiled 
from  the  "  Manual  of  American  Water-works"  for  1897  by 
Benj.  H.  Flynn,  University  of  Ohio,  class  of  '98,  for  a 
graduating  thesis.     (From  Engineering  News,  July  7,   1898.) 


3i8 


WATER-SUPPLY  ENGINEERING. 


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PURIFICATION   OF    VViiTER. 


319 


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320  WATER-SUPPLY  ENGINEERING. 

QUERIES. 

24.  What  cross-section  and  length  of  basin  would  be  required 
for  sedimentation  by  continuous  flow  if  the  consumption  were  one 
million  gallons  per  day  and  the  water  were  required  to  remain  48 
hours  in  the  basin  ?     What  capacity  for  perfect-rest  basins  ? 

25.  If  the  law  of  frictional  resistance  of  sand  to  water  holds  good 
for  clay  sediment,  what  is  the  effective  size  of  clay  particles  on  a 
certain  filter-bed  if  the  clay  sediment,  when  formed  2  inches  deep 
on  and  in  the  top  of  the  bed,  requires  an  additional  head  of  4  feet 
to  force  2,000,000  gals,  per  day  per  acre  through  the  filter? 

26.  Judging  from  the  Pittsburg  experiments,  which  of  the  two 
mechanical  filters  tested  would  be  best  for  only  slightly  turbid 
waters  ?   which  for  water  having  a  coefficient  of  turbidity  of  0.50  ? 


CHAPTER    XIV. 


PUMPING  AND   PUMPING-ENGINES. 


Art.  81.     Pumps. 

The  pumps  in  common  use  are  either  reciprocating  or 
rotary.  The  former  consists  essentially  of  a  water-chamber 
in  which  a  closely  fitting  plate  or  a  cylinder  moves  back  and 
forth.      In  Fig.  44,  B  represents  such  a  plate  (called  a  piston) 


'/r\/////y/M////:v77. 


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PISTON  PUMP 


SS^^F 


Fig.  44. — Piston-  and  Plunger-pumps. 

moved  by  a  piston-rod  (Tina  water-cylinder  A  ;  and  D  a 
plunger  (made  hollow  to  reduce  the  weight)  moving  through 
a  closely  fitting  ring  GG  in  the  cylinder  E.  Each  cylinder  is 
provided  with  openings  for  admitting  the  water  (/,  /')  and 
others  for  its  exit  ((9,  (9'),  which  are  opened  and  closed  by 
valves.  As  B  or  D  advances  to  the  left  the  water  in  L  is. 
driven  out  through  the  discharge-valve  O  and  sucked  in 
through  the  suction-valve  /,  O'  and  /'  being  closed  by  water 
pressure ;  when  B  ox  R  moves  to  the  right  water  enters 
through  /'  into  L  and  is  driven  from  R  through  O' .  /and 
/'  connect  with  a  suction-pipe,  O  and  O'  with  a  discharge- 
pipe.  If  the  surface  of  the  water  to  be  pumped  is  below  the 
cylinder,  a  vacuum  is  created  in  this  by  the  piston  or  plunger 

321 


322  WATER-SUPPLY  ENGINEERING. 

and  the  water  is  forced  in  through  the  suction-pipe  and  valves 
by  atmospheric  pressure.  A  pump  so  placed  is  called  a 
suction-pump.  But  if  the  head  above  the  cylinder  be  suffi- 
cient to  force  the  water  into  it  by  gravity  and  the  pump 
merely  raises  the  water  higher  than  itself,  it  is  called  a  lift- 
or  force-pump.  Most  pumps  are  combined  suction  and  lift. 
If  the  pump  has  two  sets  of  valves,  as  shown  in  Fig.  44,  so 
that  water  is  discharged  during  motion  in  each  direction,  it  is 
called  a  double-acting  pump.  If  the  water  is  discharged 
while  the  piston  or  plunger  moves  in  one  direction  only,  it  is 
called  single-acting.  The  ring  GG  is  called  the  bushing  or 
plunger-sleeve.  C  is  the  piston-  and  F  the  plunger-rod, 
which  pass  through  stuffing-boxes  in  the  cylinder-ends  by 
which  leakage  around  the  rod  is  prevented. 

If  a  piston-pump  cylinder  stand  upright,  and  a  valve  be 
placed  upon  the  top  of  the  piston  opening  upward,  as  in 
Fig.  45,  this  is  called  a  bucket-pump.  In  this,  water  enters 
/'and  is  discharged  through  O,  O  on  the  up-stroke;  on  the 
down-stroke  /  closes  and  water  passes  through  the  valve  F, 
which  closes  on  the  up-stroke  and  raises  the  water  which  is 
above  it.  If  the  piston-rod  C  be  of  considerable  size,  water 
will  flow  from  O,  O  during  both  down-  and  up-stroke  and  the 
pump  will  be  a  continuous-discharge  pump.  Bucket-pumps 
are  generally  used  for  deep-well  pumping. 

Upright  cylinders  on  large  engines  frequently  take  their 
water  through  the  bottom  of  the  cylinders  only,  since  these 
are  6  feet  or  more  in  height,  and  the  upper  suction-head 
would  be  greater  than  the  lower  by  a  large  part  of  this 
amount.  These  are  made  double-acting  by  supplying  the 
water-cylinder  with  a  differential  plunger.  Fig.  46.  In  this 
the  plunger  area,  d,  is  about  half  that  of  the  cylinder,  a. 
When  the  piston  descends  the  water  in  c  is  forced  into  b,  and 
half  i^asses  out  into  the  mains  while  the  other  half  enters  a. 
On  the  up-stroke  this  latter  is  forced  through  b  into  the  main, 


PUMPING   AND    PUMPING-ENGINES. 


323 


and  c  is  at  the  same  time  filled  from  the  suction-pipe.  The 
discharge  at  each  stroke  is  hence  equal  to  that  from  a  double- 
acting  pump-cylinder  of  half  the  area. 

The  force  required  to  pump  is  that  necessary  to  raise  the 
water  by  suction,  to  raise  it  by  pressure  or  lifting,  to  over- 
come the  inertia  of  all  the  water  moved,  to  overcome  the 
friction   in   the  conduits,   and  to  overcome  the  friction  and 

r 


ax 


i    V/4 


Fig.  45. — Bucket-pump  and  Disc- 
valve. 


Fig.  46. — Differential 
Plunger. 


inertia  of  the  moving  parts  of  the  pump  and  of  water  in  pass- 
ing through  the  pump.  That  required  in  suction  and  lifting 
is  the  product  of  the  weight  of  water  lifted  by  the  distance 
through  which  it  is  lifted,  and  cannot  be  altered  by  any 
mechanical  device.  The  inertia  of  the  moving  water  depends 
upon  the  mass  of  water  to  which  motion  must  be  imparted 
and  the  velocity  of  such  motion.  The  latter  can  be  decreased 
by  enlarging  the  size  of  the  pipe,  pump-cylinder,  and  other 
passages  which  the  water  must  traverse.  Friction  is  decreased 
also  by  decreasing  this  velocity.  If  the  pump  so  acts  that  at 
the  end  of  each  stroke  all  the  water  in  the  mains  comes  to 
rest,  and  must  be  given  motion  again  by  the  next  stroke,  the 


324  IVA  TER-SUPPL  Y  ENGINEERING. 

energy  required  to  overcome  the  inertia  is  considerable.  If 
the  discharge  of  water  could  be  continuous,  there  would  be 
after  the  first  few  strokes  no  inertia  to  overcome  except  that 
of  the  water  being  delivered  by  the  pump.  Various  arrange- 
ments are  used  to  obtain  this  end,  the  most  common  being 
to  so  couple  two  or  three  double-acting  pumps  together  that 
one  is  discharging  its  maximum  when  the  other  is  at  or  near 
the  end  of  its  stroke  (such  an  arrangement  being  called  a 
duplex  or  triplex  pump);  to  place  an  air-cylinder  on  the 
discharge-pipe  near  the  pump,  in  which  the  air  is  compressed 
during  the  time  of  greatest  piston-motion,  and  expands 
during  that  of  least,  thus  equalizing  the  pressure  and  conse- 
quent velocity  in  the  mains;  or  by  the  use  of  a  fly-wheel,  in 
which  the  energy  is  stored  during  mid-stroke  to  be  given  up 
by  its  inertia  at  the  ends  of  the  stroke. 

To  reduce  the  power  required  to  overcome  inertia  in  the 
moving  parts  of  the  pump  these  must  be  light  in  weight,  and 
their  motion  slow.  Their  friction  is  a  matter  of  detail  in 
design,  methods,  and  materials  of  construction,  and  of  care- 
ful maintenance.  The  friction  of  water  in  passing  through 
the  pump  may  be  considerable,  but  can  be  largely  reduced 
by  making  the  connections  between  the  cylinder  and  the 
suction-  and  force-pipes  of  ample  size  and  easy  curves,  the 
valve-openings  large  and  with  no  angles  and  well  cleared  by 
the  valves,  and  by  introducing  in  the  path  of  the  water  as 
few  obstructions  as  possible.  Another  loss,  called  slip,  exists 
to  a  certain  extent  in  all  pumps  and  is  the  water  which  escapes 
back  through  the  valves  while  they  are  closing  and  around  the 
piston  or  plunger,  and  hence  is  practically  lost  after  being 
pumped.  To  reduce  this,  which  sometimes  equals  5^  or 
mere  of  the  water  pumped,  the  valves  should  close  rapidly, 
and  the  piston  must  fit  the  cylinder,  or  the  plunger  its  ring, 
as  closely  as  is  possible  with  little  friction.  (In  the  illustra- 
tion the  valves  are  shown  as  flap-valves;    but  in  high-class 


FUMPIN'G    AND    PUMPING-ENGINES. 


325 


pumps  disc-valves  are  used,  or  discs  of  metal  or  hard  rubber 
which  rise  bodily,  and  are  generally  closed  quickly  by  springs; 
as  at  A,  Fig.  45.) 

The  pump  should  of  course  be  substantially  built  in  all  its 
parts;  should  be  so  constructed  that  contraction  and  expan- 
sion by  heat  will  not  affect  its  working;  should  be  durable, 
all  its  moving  contact-surfaces  being  automatically  lubricated  ;' 
and  should  be  provided  with  hand-holes  and  facilities  for 
reaching  all  parts  and  renewing  them  when  worn  or  injured. 

Next  to  reciprocating  pumps,  rotary  pumps  are  used  most 
extensively  for  raising  water,  the  most  common  of  these  being 
the  centrifugal  pump.  The  principle  used  in  this  pump,  as 
the  name  implies,  is  that  of  the  centrifugal  force  in  a  revolv- 
ing body.  Its  essential  parts  are  a  circular  hollow  casing  01 
"  shell,"  in  which  revolve  a  set  of  curved  arms  which  fit 
closely  the  inner  space;  the  shell  being  open  in  the  centre  on 
one  side,  as  at  /,  Fig.  47,  and  on  the  circumference  at   one 


Fig.  47. — Centrifugal  Pump. 

point,  as  O,  each  opening  forming  the  end,  /  of  a  suction-,  O 
of  a  discharge-pipe.  The  pump  being  full  of  water,  the  vanes 
(or  piston)  are  revolved ;  and  the  water,  seeking  the  circum- 
ference, is  forced  out  through  (9,  and  other  water  to  take  its 
place  enters  through  /,  and  this  operation  is  continuous  as 
long  as  the  piston  revolves.     The  flow  here  being  continuous, 


326  WATER-SUPPLY   ENGINEERING. 

there  is  no  inertia  of  water  in  the  pipe  or  of  moving  parts  to 
be  overcome  after  the  pump  is  in  motion;  the  friction  in  the 
pump,  also,  need  be  but  slight;  but  the  slip  is  considerable 
and  may  become  almost  or  entirely  lOO'l^  if  the  velocity  of 
revolution  be  too  l.w,  the  head  to  be  pumped  against  too 
great,  or  the  vanes,  or  wings,  and  the  casing  too  much  worn. 
Such  pumps  are  subject  to  little  wear,  however,  unless  the 
water  be  very  dirty.  One  of  their  disadvantages  is  the 
limited  range  of  rate  at  which  they  can  pump,  since  the 
velocity  must  be  considerable  to  prevent  slip.  They  are 
particularly  adapted  to  raising  large  volumes  of  water  short 
distances,  and  for  sediment-bearing  water.  Under  favorable 
conditions  they  are  capable  of  high  efficiency. 

Other  pumps  have  been  used  acting  upon  the  principle  of 
the  screw  of  Archimedes,  or  consisting  of  chains  of  buckets, 
and  several  other  devices;  but  it  is  not  thought  necessary  to 
consider  these  in  this  general  discussion  of  pumping  ma- 
chinery, nor  to  go  into  a  consideration  of  the  details  of  pump 
construction.  To  such  a  high  state  of  efficiency  has  the 
design  and  construction  of  pumps  been  brought  by  American 
manufacturers  that,  except  for  the  most  important  engines 
or  for  unusual  conditions,  they  may  be  trusted  to  meet  any 
stated  requirements  most  satisfactorily.  It  is  desirable,  how- 
ever, that  the  engineer  be  able  to  ascertain  whether  these 
requirements  have  been  met.  The  principal  ones  are  the 
general  solidity  and  durability  of  the  pump,  and  its  efficiency. 
The  solidity  requires  a  proper  adjustment  of  the  strength  of 
each  part  to  the  work  it  is  to  perform;  and  that  the  general 
weight  of  the  engine  and  its  foundation,  and  the  smoothness 
of  running,  be  such  that  no  vibration  be  peceptible.  Dura- 
bility demands  these  conditions  and  also  that  the  material 
be  of  the  best — castings  of  the  best  gray  iron  with  no  flaws, 
steel  tough  and  fibrous;  and  rubbing-surfaces  made  of  metals 
giving  little  friction,  generally  Tobin  bronze  or  gun-metal. 


PUMPING   AND    PUM PING-ENGINES.  327 

The   efficiency   of    a    pump   is   the    relation    between    the 

power  applied  to  it  and  the  work  performed  by  it  in  pumping 

work  done  in  pumping 

water,  or r^ — .     Each  is  fjenerally  expressed 

energy  applied  ^  ^       ' 

in  foot-pounds,  and  the  efficiency  is  hence  an  abstract  number. 
The  work  done  is  ascertained  by  multiplying  the  weight  of 
water  by  the  entire  distance  through  which  it  is  raised, 
including  both  suction  and  lift,  and  adding  the  friction  in  all 
pipes  or  that  due  to  any  other  causes  outside  of  the  pump. 
To  allow  for  this  outside  friction  the  head  is  generally  taken  as 
that  indicated  by  the  sum  of  the  pressure  in  the  discharge- 
pipe  and  vacuum  in  the  suction-pipe,  both  referred  to  the 
same  level.  That  is,  if  the  vacuum-gauge  on  the  suction-pipe 
is  three  feet  below  the  pressure-gauge  on  the  delivery-pipe, 
and  these  two  read  20  feet  and  100  feet  respectively,  the 
total  head  of  123  feet  is  used  in  the  calculation.  The  energy 
applied  is  measured  by  a  transmission-dynamometer,  or  some 
other  contrivance  whose  character  is  adapted  to  the  method 
of  applying  the  power. 

Art.  82.     Pumping-engines. 

Rotary  pumps  are  generally  driven  by  belting  or  gearing 
from  a  steam  or  other  engine,  or  by  water  or  electric  motors 
mounted  upon  the  shaft  of  the  pump. 

Reciprocating  pumps  may  be  driven  either  by  belting, 
gearing,  or  motor,  when  they  are  called  power-pumps;  or 
they  maybe  direct-acting,  that  is,  the  piston-rod  of  the  pump 
may  have  upon  its  other  end  another  piston  working  in  a 
cylinder  and  actuated  by  steam  or  other  medium;  or  the 
power  may  be  applied  by  an  engine  through  the  medium  of 
a  crank-shaft  supplied  with  a  fly-wheel. 

Water  is  a  practically  non-elastic  fluid,  and  "while  this  is 
met  in  the  direct-acting  type  of  steam-pump  by  the  elastic 


328 


WATER-SUPPLY  ENGIXEEPIATG. 


steam-cushion,  the  load  in  the  power-pump  is  received  fully 
on  the  crank-pin  as  it  passes  the  centre.  Therefore  in  the 
power-pump  the  bed-plate  must  be  so  constructed  as  to  with- 
stand this  excessive  strain  and  vibration.  The  foundations 
must  also  be  of  the  most  substantial  character,  all  working; 
parts  must  be  of  unusual  strength,  and  suitable  means  of 
adjustment  to  compensate  for  wear  must  be  provided.'* 
(Chas.  L.  Newcomb.) 

In  the  direct-acting  pump,  B,  any  shock  communicated 
by  the  water,   stoppage  in  the   water-end,  or   break   in  the 


Fig.  48. — Power,  Direct-acting,  and  Fly-wheel  Pumps. 
delivery-pipe  and  consequent  release  of  pressure,  is  largely 
taken  up  by  the  steam  acting  as  a  cushion  in  the  steam- 
cylinder.  In  the  case  of  the  fly-wheel  pump,  the  wheel  takes 
the  shock  and  little  is  felt  by  the  motive  engine;  but  the 
length  of  stroke  of  the  steam-end  is  fixed  and  this  is  for  some 
reasons  an  objection.  In  the  power-pump,  A,  when  gearing^ 
is  used  the  engine  and  intermediate  gearing  are  both  apt  to 
be  wrecked  by  a  sudden  stoppage  in  the  water-end.  For  this 
reason  a  belt  instead  of  gearing  is  often  used,  its  disadvantage 
being  the  larger  amount  of  space  necessary,  10  to  20  feet  at 
least  being  required  by  the  belting  alone.  "A  higher  piston- 
speed  can  be  had  with  a  crank  and  fly-wheel  pump  than  if 
the  pump  were  direct-acting,  for  the  reason  that  in  the  latter 
type  the  termination  of  each  stroke  is  defined  and  secured  by 
steam  acting  as  a  cushion  to  counteract  the  force  of  the 
moving  parts  of  the  water.  In  large  steam-pumps  100  feet 
per  minute  may  be  considered  as  the  limit  to  safe  piston- 


PUMPING   AND    PUMPING-ENGINES.  329 

speed.  With  pumping-engines  having  cranks,  connecting- 
rods  with  tly-wheels  to  terminate  and  define  the  stroke  of  the 
piston,  any  piston-speed  possible  to  the  pumps  can  be  secured 
with  safety.  The  power  stored  in  the  moving  mass  of  the 
fly-wheel  at  the  termination  of  the  stroke  is  carried  to  the 
beginning  of  the  next  stroke  without  any  loss  but  that  due  to 
the  friction  of  the  moving  parts  and  the  resistance  of  the  air 
to  the  motion  of  the  fly-wheel.  Then  the  practically  uniform 
speed  of  the  rim  of  the  fly-wheel  secures  the  desired  motion 
for  the  piston  through  the  connecting-rod  and  crank  of  the 
pump  by  gradually  retarding  the  motion  until  the  point  of 
rest  is  reached,  and  accelerating  it  after  the  piston  has  passed 
that  point."  (H.  P.  M.  Birkenbine.)  The  definite  length  and 
termination  of  stroke  are  obtained  by  the  power-pump  also. 

If  we  consider  the  two  cylinders  and  pistons  in  B,  Fig.  48, 
it  is  evident  that  the  total  pressure  on  the  steam-piston  is 
practically  the  same  as  that  upon  the  water-piston.  Hence 
the  pressure  per  square  inch  on  each  is  inversely  as  the  areas 
of  the  pistons.  Thus,  if  the  diameter  of  the  water-piston  be 
15  inches  and  that  of  the  steam-piston  be  12,  and  the  pressure 
per  square  inch   in   the  water  end   be  100  lbs.,  that   upon   the 

steam  end  must  be  =^   X   100  =  156  -|-  lbs.  per  square  inch, 
12' 

and  somewhat  more  than  this  steam-pressure  must  be  main- 
tained in  the  boilers.  When  the  piston  has  reached  the  end 
of  the  stroke  the  steam-pressure  must  still  be  1.56  times  the 
water-pressure.  There  is  still,  however,  energy  remaining  in 
the  steam  which  could  be  utilized  in  expansion  under  less 
pressure.  To  effect  this,  the  exhaust-steam  (that  escaping 
from  the  cylinder  at  the  end  of  the  stroke)  is  conducted  to 
another  cylinder  whose  piston  has  three  to  five  times  the  area 
of  the  first  and  on  which  consequently  the  pressure  is  but  one 
third  to  one  fifth  of  156  lbs.  per  square  inch,  and  the  steam 
can  here  expand  until  exerting  only  this  pressure,  when   it  is 


330  WATER-SUPPLY  ENGIiXEERING. 

allowed  to  escape.  In  some  cases  still  a  third  cylinder  larger 
than  the  second  is  used  to  utilize  further  expansion.  Such 
an  engine  is  called  a  compound  if  there  be  two  cylinders,  a 
triple-expansion  if  there  be  three.  The  first  cylinder  is  called 
the  high-pressure,  the  last  the  low-pressure;  if  there  be  three, 
the  middle  is  called  the  intermediate  cylinder  (see  Fig.  50, 
page  343).  The  exhaust-steam  from  the  low-pressure  cylin- 
der may  be  condensed  by  spraying  cold  water  through  it,  or 
by  passing  it  over  pipes  kept  cool  by  water  flowing  through 
them,  and  a  vacuum  is  thus  produced  in  the  low-pressure 
cylinder  which  adds  still  more  energy.  Compounding  an 
engine  adds  about  20^  to  the  energy  derived  from  a  given 
amount  of  steam;  and  condensing,  about  20fo  more;  and  the 
third  condensing-cylinder  still  further  increases  the  efficiency 
of  the  engine  in  its  use  of  steam.  A  high-duty  engine — that 
is,  one  of  high  efficiency — must,  to  be  so  considered  at  the 
present  time,  be  compound  or  triple-expansion,  condensing, 
and  the  pump-end  duplex  or  triplex;  in  addition  to  which  a 
fly-wheel  or  an  equivalent  "  high-duty  attachment"  is  gen- 
erally required.  The  latter  is  a  method  of  storing  energy  at 
one  part  of  the  stroke  and  using  it  at  another  by  the  com- 
pression of  water  in  a  strong  cylinder  instead  of  by  a 
fly-wheel. 

A  small  engine  is  usually  constructed  with  horizontal 
cylinders,  since  it  can  thus  be  made  more  solid  at  less 
expense.  But  if  the  pistons  and  rods  are  very  large  and 
heavy  the  friction  upon  their  lower  side  causes  unequal  wear, 
and  the  rods  may  sag;  larger  foundations  are  required;  and 
for  other  structural  reasons  it  is  preferable  to  place  the  cylin- 
ders vertical,  the  steam-cylinders  being  placed  above  the 
water-cylinders.  These  are  called  vertical,  as  distinguished 
from  horizontal,  engines.  An  additional  advantage  in  their 
use  occurs  when  the  pump  is  placed  beneath  the  ground- 
surface,  since  the  steam-cylinders  are  then  nearer  the  surface 


PUMPING    AND    PUMPING-ENGINES.  331 

and  the  boilers,  and  the  pump-pit  may  be  made  compara- 
tively small. 

So  intimately  are  the  pump  and  its  motor  generally  con- 
nected that  the  whole  is  called  a  pumping-engine,  is  generally 
furnished  by  the  same  builder,  and  its  efficiency  as  a  whole  is 
that  ordinarily  required  and  determined. 

A  great  majority  of  the  pumping-plants  at  present  in 
service  use  steam  as  a  motive  power,  and  these  will  be  first 
considered. 

Art.  83.     Duty  of  Pumping-engines. 

In  a  steam-engine  the  applied  energy  is  the  amount  of 
heat  contained  in  the  steam  which  reaches  the  engine.  The 
efficiency  of  an  engine  is  stated  as  its  duty,  which  equals  the 
amount  of  work  done  in  pumping  divided  by  ^^^^^^^^^  of  the 
heat-units  furnished,  or  y^V(7  ^^  ^^^  pounds  of  dry  steam, 
whichever  is  specified.  It  is  assumed  that  one  pound  of 
steam  furnishes  looo  heat-units,  but  this  amount  varies,  and 
the  most  accurate  and  reliable  method  is  the  use  of  heat- 
units,  the  "British  thermal  unit  "  being  that  generally  used. 
The  duty  is  described  as  foot-pounds  of  work  per  looo  lbs. 
of  moist  steam,  per  lOOO  lbs.  of  dry  steam,  or  per  1,000,000 
B.T.U.  (A  British  thermal  unit  is  the  amount  of  heat 
necessary  to  raise  one  pound  of  water  at  its  maximum  density 
through  one  degree  Fahr.) 

That  these  methods  do  not  all  give  the  same  result  is 
seen  by  the  following  table  giving  the  result  of  a  test  made 
of  a  i6-million-gallon  pumping-engine  designed  by  E.  D. 
Leavitt  and  built  by  the  I.  P.  Morris  Co. 

In  this  case  one  pound  of  dry  steam  furnished  about  1075 
heat-units.  (If  water  is  carried  over  into  the  steam-pipes  by 
the  steam  from  the  boiler,  or  is  formed  in  them  by  condensa- 
tion, this  furnishes  no  energy  and   should  be  deducted   from 


332 


WATER-SUPPLY  ENGINEERING. 


the  weight  of  the  steam.      This  reduced  weight  is  referred  to 
in  the  following  table  under  the  head  of  "  dry  steam,") 


DUTY    OF    PUMPING-PLANT. 


Day. 


First  .. 
Second. 
Third.. 

Fourth 
Fifth... 
Sixth  .. 


Ft. -lbs.  per 

loo  lbs.  Dry 

Pittsburg  Coal. 


117,192,000 
130,170,000 
129,854,000 


Per  100  lbs. 

Dry  Pocahontas 

Coal. 


132,208,000 
140,747,000 
144,676,000 


Per  100  lbs. 

Pittsburg 

Combustible. 


120,504,000 
i33.S95.OOO 
134,464,000 


Per  100  lbs. 
Pocahontas 
Combustible. 


138,516,000 
147,015,000 
152,370,000 


DUTY    OF    PUMPING-ENGINE. 


Day. 


First  . . 
Second 
Third. 
Fourth 
Fifth.. 
Sixth  . 


Per  1,000,000 
Heat-units. 


138,008,000 
137.525,000 
137,948,000 
137,387,000 
138,274,000 
136,260,000 


Per  1000  lbs. 
Moist  Steam. 


148,285,000 
147,892,000 
148,195,000 
147,667,000 
148,538,000 
146,459,000 


Per  1000  lbs. 
Dry  Steam. 


149,104,000 
148,710,000 
149,014,000 
148,483,000 
149,360,000 
147,269,000 


The  total  number  of  B.T.U.  in  steam  is  represented  by 
the  equation 

77=  i092  +  o.3(r—  32°)=  1146  +  0.3(7^—  212°), 


in  which  T  is  the  temperature  of  the  steam  in  degrees  Fahr. 
The  available  energy  is  that  due  to  H  —  h,  when  h  is  the 
number  of  B.T.U.  in  the  steam  which  leaves  the  cylinder. 
The  latent  heat  of  evaporation  of  steam  =  g66  B.T.U.  when 
under  one  atmosphere  of  pressure,  or  when  the  pressure  is 
14.7  lbs.  per  square  inch.  If  the  pressure  is  greater  the 
evaporating-point  is  higher,  as  is  shown  in  Table  No.  6y,  the 
first  and  second  columns. 


PUMPING   Ai\D    PUMPING-ENGINES. 


333 


Table  No.  67. 
latent  heat  of  evaporation. 


d 

c 
'0 

Initial  Temperature  of  Feed-water  ("  from") 

"J 

3 

a. 

'0^ 
03 

32° 

so" 

68° 

86° 

104° 

122° 

140" 

is8» 

176° 

'94° 
1.02 

218" 

14.7 

212° 

1. 19 

1. 17 

I.T5 

I-I3 

I. II 

1. 10 

1.08 

1.06 

1.04 

I. 00 

20.8 

230 

1.20 

1. 18 

1. 16 

1.14 

1. 12 

1. 10 

1.08 

1.06 

1.04 

1.02 

I. 01 

28.83 

24S 

1.20 

1. 18 

1. 16 

1. 14 

1. 13 

I. II 

1.09 

1.07 

1.05 

1.03 

I. 01 

39-25 

266 

1. 21 

1. 19 

1. 17 

I-I5 

1. 13 

I. II 

1.09 

1.07 

1.06 

I   04 

1.02 

52.52 

284 

1. 21 

1.20 

1. 18 

1. 16 

1. 14 

1. 12 

1. 10 

1.08 

1.06 

1.04 

1.02 

69.21 

302 

1.22 

1.20 

1. 18 

1. 16 

1. 14 

1. 12 

I. II 

1.09 

1.07 

1.05 

1.03 

89.S6 

320 

1.22 

1.21 

1. 19 

1.17 

I-I5 

1. 13 

I. II 

1.09 

1.07 

1.05 

1.03 

115.1 

338 

1.23 

1. 21 

1. 19 

1. 17 

1. 15 

1. 14 

1. 12 

1. 10 

1.08 

1.06 

1.04 

145. 8 

356 

1.23 

1.22 

1.20 

1. 18 

1. 16 

1. 14 

1. 12 

X.IO 

1.08 

1.06 

1.04 

182.4 

374 

r.24 

1.22 

1.20 

1. 18 

1. 17 

1. 15 

I-I3 

1. 11 

1.09 

1.07 

1.05 

225.9 

392 

1.24 

1.23 

1. 21 

1. 19 

1. 17 

I-I5 

1. 13 

I. II 

1.09 

1.07 

I. 06 

276.9 

410 

1.25 

1.23 

1.22 

1.20 

1. 18 

1. 16 

1. 14 

1. 12 

1. 10 

1.08 

1.06 

336.3 

428 

1.25 

1.24 

1.22 

1.20 

1.18 

1. 16 

1. 14 

1. 12 

I. II 

1.09 

1.07 

The  higher  the  evaporating-point  the  greater  the  amount 
of  latent  heat  in  the  steam ;  it  being  4^  greater  when  the 
pressure  is  115  lbs.,  for  instance,  than  when  it  is  14.7  lbs., 
as  is  shown  by  the  above  table.  It  takes  a  certain  amount 
of  heat,  or  number  of  heat-units,  to  raise  the  temperature  of 
water  each  degree.  Hence  the  number  of  pounds  of  water 
which  can  be  evaporated  by  a  given  amount  of  heat  depends 
upon  the  original  temperature  and  that  of  the  steam,  which 
latter  varies  with  the  boiler-pressure.  In  order  to  compare 
different  tests,  the  actual  duty  performed  by  coal  in  a  given 
test  is  reduced  to  that  it  would  have  performed  had  the  water 
been  at  a  temperature  of  212°  Fahr.  when  reaching  the 
boiler.  If  the  temperature  of  the  water  be  lower  than  212°, 
or  the  pressure  more  than  14.7,  more  heat-units  will  be 
required.  As  an  illustration  of  the  use  of  Table  No.  6'j :  if 
one  pound  of  coal  evaporate  8  lbs.  of  water  whose  original 
temperature  was  50°,  the  steam-pressure  being  182.4  lbs.  per 
square  inch,  the  work  done  was  equivalent  to  evaporating 
1.22  times  8  lbs.,  or  9.76  lbs.,  from  and  at  212°. 


334  WATER-SUFPLY  ENGINEERING. 

The  efficiency  of  the  boiler  which  generates  the  steam  is 
of  nearly  as  great  importance  as  that  of  the  pumping-engine; 
and  a  high  efficiency  of  the  entire  plant — boiler,  steam-pipes, 
engine,  and  pump — acting  together  is  the  end  sought.  In  a 
majority  of  cases  this  total  efficiency  is  guaranteed  by  one 
firm,  which  furnishes  the  entire  plant  in  running  order;  and  this 
efficiency  is  that  determined,  although  generally  that  of  the 
separate  portions  is  ascertained  also.  This  total  efficiency  or 
duty  is  expressed  as  foot-pounds  of  work  per  lOO  lbs.  either 
of  coal  or  of  combustible  matter  in  the  coal,  or  per  1,000,000 
heat-units  in  the  coal.  The  efficiency  of  the  boiler  alone  is 
expressed  in  the  number  of  pounds  of  steam  formed  for  each 
pound  of  coal  burned,  or  for  each  pound  of  combustible 
matter  in  such  coal.  The  former  is  found  by  weighing  the 
steam  and  the  coal  used  in  producing  it;  the  latter  by  deduct- 
ing from  the  weight  of  coal  that  of  the  ashes  remaining.  In 
the  test  tabulated  on  page  332  the  ashes  on  the  first  day  formed 

120,504,000—       117,192,000  ,  f  ,  T^. 

• '-±— — or  2.7  4-  per  cent  of  the   Pitts- 

120,504,000  ^ 

burg  coal,  and  on  the  fourth  day  4.7  -|-  per  cent  of  the 
Pocahontas  coal.  One  pound  of  Pittsburg  coal  was  found  to 
supply  about  9250  heat-units  and  to  evaporate  8.60  lbs.  of 
water;  while  one  pound  of  Pocahontas  coal  supplied  10,294 
heat-units  and  evaporated  9.57  lbs.  of  water.  Different  coals 
may  vary  30^  in  their  "  calorific  efifect,"  or  available  heat- 
units.  Eureka  Clearfield  bituminous  coal  has  been  found  to 
contain  15,174  B.T.U.  by  calorimeter  tests. 

It  is  desirable  to  supply  water  to  the  boiler  as  warm  as 
may  be  without  increased  expense,  and  this  is  effected  by  a 
feed-water  heater  or  economizer,  in  which  a  part  of  the  heat 
escaping  from  the  fire  into  the  flue  and  otherwise  wasted  is 
utilized  to  heat  the  water  which  is  being  supplied  to  the 
boiler.  A  portion  of  the  heat  in  the  exhaust-steam  is  used 
for  the  same  purpose,  also.     To  prevent  radiation  from  and 


PUMPIXG   AXD    PUM PING-ENGINES. 


335 


condensation  in  the  steam-cylinders  of  high-duty  pumps, 
steam  is  passed  continually  around  them  in  "jackets,"  and 
from  these  it  passes  either  directly  to  the  boiler,  or  to  a 
"  hot  well  "  from  which  it  is  pumped  into  the  boiler  by  the 
feed-water  pump.  Other  minor  appliances  are  used  for  de- 
creasing loss  of  heat  by  radiation  from  boiler,  steam-pipes, 
pumps,  etc.,  or  for  utilizing  such  heat. 

To  understand  and  study  the  energy  furnished,  utilized, 
and  lost  in  a  steam-plant,  it  should  be  borne  in  mind  that 
steam  is  but  an  agent  for  utilizing  heat,  and  that  all  the  heat 
furnished  by  the  fire  can  and  should  be  accounted  for  in  a 
test.  The  following  details  of  the  test  above  referred  to  are 
here  given,  accompanied  by  a  graphic  representation  of  the 
same  facts,  prepared  from  the  data  by  Capt.  H.  R.  Sankey 
and  presented  by  him  in  a  report  to  the  Institution  of  Civil 
Engineers.  It  is  thought  that  a  careful  study  of  these,  and 
particularly  of  the  diagram,  will  be  of  great  value  in  getting 
clearly  in  mind  the  losses  in,  and  efficiency  of,  the  various 
parts  of  a  steam  pumping-plant. 


RN  FROM  JACKETS 


ECONOMIZER.   j, 
80160      ^yy"', 
FLUE  LOSS 


>       1870 
J.  .    ^fENOINE  FRICTrOrf 

'^ ■  ■     ■■.■/  •fe-^'-       25390 

«  WJR.     NPrsibXS^.^  EFFECTIVE 

-^-^•^-WORK  BRAKE  H.P. 


RADIATION 
>  4600 
FROM  ENOINE 


Fig.  49.— Losses  of  Heat  in  a  Steam  Pumping-plant, 

"  Starting  at  the  fire-grate,  it  is  shown  that  183,600 
B.T.U.  are  produced  per  minute  by  the  combustion  of  the 
coal,  and  that  131,700  of  these  go  direct  into  the  water  of  the 
boiler,    10,000  are  lost  by  boiler-radiation  and  leakage,  and 


336  WATER-SUPPLY  ENGINEERING. 

the  remainder,  viz.,  41,900,  pass  away  with  the  flue-gases. 
On  the  way  to  the  economizer  lOOO  B.T.U.  are  lost  by  radia- 
tion, but  in  the  economizer  itself  15,750  B.T.U.  are  diverted 
into  the  feed-water,  5000  B.T.U.  are  dissipated  by  radiation, 
and  finally  20,150  B.T.U.  pass  out  of  the  economizer  and 
into  the  chimney,  and  are  lost  to  the  steam-plant.  The  heat 
entering  the  economizer  with  the  feed-water  is  5450  B.T.U., 
which  is  added  to  the  15,750  B.T.U.  diverted  from  the  flue- 
gases,  thus  giving  a  flow  of  21,200  B.T.U.  in  the  feed  out  of 
the  economizer.  Radiation,  however,  reduces  this  flow  to 
20,950  B.T.U.  per  minute  at  the  entry  to  the  boiler,  where 
a  further  addition  is  made  of  6600  B.T.U.  returned  by  the 
jacket-water. 

"  The  steam  produced  by  the  boiler  is  thus  seen  to  derive 
its  heat  from  three  streams,  as  shown  in  the  diagram;  the 
steam  finally  leaves  the  boiler  with  159,250  B.T.U.  per 
minute.  Before  this  heat  gets  to  the  engine,  however,  3100 
B.T.U.  are  lost  by  radiation  and  leakage  from  the  steam- 
pipes,  so  that  the  flow  of  heat  is  reduced  to  156,150  B.T.U. 
per  minute,  which  is  the  gross  supply  of  heat  to  the  engine; 
the  net  supply  is  less,  because  there  are  certain  returns  of 
heat  to  the  boiler  to  be  deducted.  In  the  first  place  credit 
has  to  be  given  to  the  engine  for  the  heat  which  could  be 
imparted  by  means  of  the  exhaust-steam  to  the  feed-water, 
inasmuch  as  the  exhaust  is  theoretically,  and  very  nearly 
practically,  capable  of  raising  the  temperature  of  the  feed  to 
the  exhaust  temperature.  On  this  basis  7400  B.T.U.  should 
be  credited  to  the  engine.  Although  the  actual  return  to 
the  boiler,  or  rather  to  the  economizer,  is  only  5450  B.T.U," 
(H.  R.  Sankey.) 

Of  the  6750  "return  from  jackets  "  the  150  lost  by  radia- 
tion should  be  charged  against  the  engine,  since  the  jackets 
are  supplied  to  correct  a  fault  in  the  engine,  viz.,  cylinder- 
condensation.     This  leaves  142,150  B.T.U.  as  the  net  supply 


PUMPING   AND    PUMPING  ENGINES.  33/ 

to  the  engine.  Of  this  117,640  departs  in  the  exhaust  with- 
out yielding  any  of  its  energy,  and  the  remainder,  or  27,260 
B.T.U.,  goes  into  work  in  the  engine.  Of  this,  1870  is  con- 
sumed in  the  internal  friction,  leaving  the  actual  work  done 
in  pumping  due  to  25,390  B.T.U.  The  thermal  ef^ciency 
of  any  part  of  the  plant  can  now  be  readily  determined,  and 
is  the  ratio  of  the  number  of  B.T.U.  applied  to  those 
delivered    as    heat    or   work.      Thus    that    of    the   engine    is 

27,260  ,  ,  .         ,  ,         ,     ,  25,390 

=  o.  19  +  ;  or,  takmg  the  actual  work  done, — 

142,150  ^    '  "^  142,150 

=   .18  — ,    the    per    cent    of    applied    energy    utilized.      The 

thermal    efificiency   of   the   boiler,    economizer,    and    grate    is 

159,250 

—^ — -p ; ; — ^^ —  =  .8ii;    and    of    the    entire    plant 

183,600  +  5450  +  6600  ^  ^ 

25,390 

—z — ■:;: —  =:  .lA.—  .  The  mechanical  efficiency  of  the  pump  is 
183,600  ^  J  f       f 

25-390  ,  , 

■ ^,  or  .93  +  . 

27,260  ^"^  ' 

The  following  are  some  of  the  data  obtained  in  the  test 
of  this  engine: 

STEAM    USED    BY    ENGINE    AND    FEED-PUMP  ;    ENTIRE    TEST    OF 
144    HRS.     10    MIN. 

(i)  Weighed  feed-water 968,128  lbs 

(2)  Feed-pump  steam,  condensed 23,390    " 

(3)  Total  water  pumped  into  boilers 991,518     " 

(4)  Total  water    returned   to   boilers   from  jackets 

and  reheaters 189,795     " 

(5)  Sum  of  (3)  and  (4) 1,181,313     " 

\t)  Total  steam  used  by  calorimeter 727    ' 

(7)  Total  water  drained  from  separator 23,428     " 

(8)  Total    moist   steam    used    by   engine  and   feed- 

pump   1,157,158     '* 

(9)  Percentage  of   moisture   in  steam   after  leaving 

separator 0.55!? 

(10)  Total  dry  steam    used   in  engine  and  feed-pump 

(=  99.45^  of  (8)  ) 1,150,792  lbs. 

STEAM    USED    KY    ENGINE. 

(11)  Total  moist  steam  used  by  engine  only 1,133,768  lbs. 

(12)  Total  dry  steam  used  by  engine  only I>i27,533  lbs. 


338  WATER-SUPPLY  ENGINEERING. 

(13)  Total  moist  steam  passing  through  cylinders...  943.973  lbs. 

(14)  Total  moist  steam  passing  through  jackets   and 

reheaters 189,795  lbs. 

(15)  Percentage  of  moist  steam   used  by  jackets  and 

reheaters 16.74^ 

(16)  Moist   steam    used   per   hour   per   I.H.P.     (indi- 

cated  horse-power)  * 12.223  lbs. 

(17)  Dry  steam  used  per  hour  per  I.H.P. * I2.i5t)  lbs. 

(18)  Dry  steam  passing  through  cylinders  per  hour 

per  I.H.P 10.120  lbs. 

(19)  Dry  steam  used  per  hour  per  pump  H.P.* 13.050  lbs. 

B.T.  U.   SUPPLIED    BY    BOILERS. 

(20)  Heat  of  vaporization,  Steam  154.6  lbs.,  absolute  t  859.4  B.T. U. 

(21)  Heat  of  liquid,  steam   154.6  Ibs.f 332.5  B.T.U. 

(22)  Heat  of  liquid  feed,  143.30 111.5  B.T.U. 

(23)  Per  pound  of    moist    steam  supplied  by    boilers 

(859-4  X  .99454-332-5  -  II  1.5  =) 1. 075-7  B.T.U. 

(24)  Total  supplied  by  boilers, 

((5))  1,181,313X1075.7=    1,270,738,600  B.T.U. 

(25)  Total  supplied  by  boilers  per  minute 146,903  B.T.U. 

B.T.U.    USED    BY    THE    ENGINE. 

(26)  Per  pound  of  moist  steam  used  by   the  cylinders  II34-5  B.T.U. 

(27)  "         "       "        "         "  "     in  jackets  and  re- 

heaters    880.8  B. T. U. 

(28)  Used  by  engine  during  trial 1,238,108,959  B.T.U. 

(29)  "       "  "       per  minute 143,134  B.T.U. 

(30)  "       ' "      per  I.H.P 222.46    B.T.U. 

(31)  Average  mean   effective  pressure  in  high-pres- 

sure cylinder 

(32)  Average   mean    effective   pressure   in  low-pres- 

sure cylinder 

(33)  H.P.  developed  in  H.P.  cylinder 

(34)  H. P.  "  "    L.P.  cylinder 

(35)  H.P.  lost  in  friction 

(36)  Efficiency  of  mechanism 

FUEL. 

Coal. 
Pittsburg.         Pocahontas. 

(37)  Moist  coal  consumed,  lbs 67,917  63,591 

(38)  Wood  consumed  at  50  per  cent  weight,  lbs.. ... .  772  25 

(39)  Moisture  in  coal,  per  cent 0.7  2.6 

(40)  Dry   coal   consumed  with  wood   equivalent,  lbs.  67,995  61,692 

♦  I.  H.  P.,  the  energy  utilized  as  work  on  the  pistons,  represented  in  the  diagram  by 
27,»6o  B.T.U.  Pump  H.P.,  the  energy  dehvered  by  the  pump  in  work,  represented  as  25,390 
B.T.U.  per  minute. 

•t  Note  that  the  sum  of  (20)  and  (21),  or  total  heat  units,  gives  the  same  result  as  the  formula 
for  H;  the  temperature  of  the  steam  being  365", 


43-53 

lbs. 

14-155 

lbs. 

279.00 

364-40 

44.30 

93.12 

jer  cent 

PUMPING   AND    PUMPING-ENGINES.  339 

(41)  Total  ash,  dry,  lbs 2,025  2,8419 

(42)  Total  combustible,  lbs ^5,970  58,843 

(43)  Calorific  value  of  one  pound  of  coal  by  analysi 

B.T.U 13,226  14.924 

(44)  Water  actually   evaporated    per   pound   cf    dry 

coal,  lbs 8.60  9.57 

(45)  Equivalent  water  evaporated  per  pound  of   dry 

coal,  from  and  at  212°,  lbs g.63  10.70 

(46)  Equivalent  total   heat  derived  from  a   pound  of 

dry  coal,  B.T.U 9.250  10,294 

(47)  Water  actually  evaporated  per  pound  of  combust- 

ible,  lbs 8.86  10.03 

(48)  Equivalent  water  evaporated  per  pound  combust- 

ible, from  and  at  212°,  lbs 9-92  n.22 

(49)  Efficiency  of  boilers,  per  cent    (=  ) 70.0  60.0 

\      (43)/ 

(50)  Dry  coal  burned  per  sq.  ft.  of  grate  per  hour,  lbs.  12.70  11.50 

(51)  Coal  used  per  I.  H.P.  per  hour,  lbs 1.47  1.33 

(52)  Coal  used  per  pump  H.  P.  per  hour,  lbs r.58  1.43 


This  test,  conducted  by  F.  W.  Dean  and  Dexter  Brackett 
in  April  1894,  was  continuous  for  144  hours  and  lo  minutes. 
The  engine  was  regarded  by  Mr.  Dean  as  "  the  most 
economical  compound  engine  that  has  ever  been  tested." 
Its  duty  of  137,565,000  ft. -lbs.  per  1,000,000  B.T.U.  has 
been  exceeded  by  triple-expansion  engines,  however;  and 
Geo.  H.  Barrus  considers  155  or  even  160  million  foot-pounds 
as  possible  of  attainment.  The  table  on  next  page  was 
prepared  by  him,  and  brings  records  of  high-duty  engines  up 
to  December  1898. 

From  the  definition  of  duty  it  is  evident  that  theoretically 
an  engine  having  a  duty  of  100,000,000  will  consume  but 
half  as  much  coal  as  one  having  a  duty  of  50,000,000.  And 
this  will  be  practically  the  case  if  there  be  in  charge  experi- 
enced engineers  and  firemen  who  can  and  will  constantly  keep 
both  boiler  and  engine  working  at  their  best.  If  such  men 
are  not  placed  in  charge  it  is  doubtful  whether  a  high-duty 
pump  should  be  used,  as  it  is  more  liable  than  a  low-duty  to 
be  ruined  by  careless  treatment,  and  under  such  treatment 


340 


WA  TEH-SUP  PL  Y  ENGINEERING. 


PUMPING    AND    PUMPING-ENGINES. 


341 


■may  not  realize  more  than  50  to  75  per  cent  of  its  full 
efficiency.  In  any  particular  case  the  interest  on  the  cost 
and  the  depreciation  of  a  low-,  medium-,  and  high-duty 
pump,  with  the  cost  of  coal,  engineer's  and  fireman's  salaries, 
and  other  expenses  of  each  should  be  compared  with  those 
of  the  other,  and  that  which  shows  the  least  annual  cost  will 
be  the  most  economical.  With  pumps  of  a  capacity  less  than 
300,000  to  500,000  gals,  per  day,  single-expansion,  or  simple, 
engines  alone  are  ordinarily  made,  and  the  duty  is  seldom 
greater  than  38,000,000  or  40,000,000.  Above  this  size  com- 
pound duplex  pumps  are  generally  used  ;  and  horizontal  triple- 
expansion  pumps  (see  Fig,  50,  page  343)  are  made  of  a 
capacity  of  750,000  to  5,000,000  gals,  daily.  Vertical 
engines  are  made  of  all  sizes,  but  horizontal  are  now  seldom 
made  larger  than  5,000,000  gals.  A  compound  condensing 
direct-acting  engine  can  be  obtained  with  a  duty  of  50  to  125 
million  foot-pounds,  depending  upon  its  size;  and  75  to  160 
million  is  obtained  with  triple-expansion  engines  of  i  to  30 
million  gallons  capacity. 

The  duty  possible  of  attainment  depends  in  some  degree 
upon  the  pressure  of  steam  in  the  boiler.  Charles  A.  Hague 
states  that  the  different  steam-pressures  will  cause  the  follow- 
ing differences  of  duty  in  the  same  engine. 


Steam-pressure. 

Duty  per  looo  lbs.  of  Steam. 

Compound  Engine. 

Triple-expansion  Engine. 

75 
80 

104,000,000 
106,000,000 
108,000,000 
110,000,000 
112,000,000 
114,000,000 

90 
100 
no 
120 
129 
141 

125,000,000 
126,000,000 
128,000,000 
130,000,000 
134,000,000 

342  WATER-SUPPLY  ENGIiVEEPrNG. 

The  duty  of  an  engine  is  also  reduced  by  reducing  its 
work.  It  is  hence  inexpedient  to  call  for  an  engine  of  much 
greater  capacity  than  that  which  is  actually  required.  "  A 
properly  designed  pumping-engine  will  work  with  water- 
pressures  from  lO  to  25  per  cent  higher  than  the  nominal 
pressure,  without  appreciably  falling  off  in  economy;  but  if 
the  water-pressures  are  from  10  to  25  per  cent  less  than  the 
engine  was  designed  for,  the  falling  off  in  economy  becomes 
very  marked."  (I.  H.  Reynolds.)  It  is  hence  desirable  that 
the  specified  duty  be  required  at  ordinary  working  pressure 
and  speed,  but  that  the  pump  be  guaranteed  to  safely  work 
under  maximum  conditions. 

Engines  under  working  conditions  seldom  attain  the  duty 
found  by  the  test,  as  might  be  expected.  But  they  can  be 
kept  up  to  90^  of  this  when  in  good  condition,  by  careful, 
intelligent  management.  Boilers  of  the  Brooklyn  Water- 
works evaporated  10.94  lbs.  of  water,  at  and  from  212°,  per 
pound  of  Eureka  coal,  in  1895.  The  pumping-plant  at 
Newton,  Mass.,  worked  with  an  average  annual  efificiency  of 
110,000,000  ft.-lbs„  per  100  lbs.  of  coal.  On  the  other  hand, 
the  effect  of  wear  and  necessity  of  renewing  pumping-plants 
which  have  been  outgrown  is  shown  by  that  at  Taunton, 
Mass.,  which  attained  an  average  duty  of  53,406,265  ft. -lbs. 
in  1893,  37,837,519  in  1895,  and  but  34,096,561  in  1896. 

Art.  84.     Arrangement  of  Pumping-engines. 

Horizontal  compound  engines  are  made  with  the  low- 
pressure  cylinder  either  between  the  high-pressure  and  the 
water  end,  or  in  the  reverse  order.  In  the  former  case 
the  smaller  high-pressure  cylinder  is  generally  made  to  over- 
hang the  base,  and  thus  reduce  the  length  of  foundation 
necessary.  In  fact,  the  reduction  of  cost  made  possible  by 
this  is  about  the  only  advantage  of  this  arrangement;    and 


PUMPIXG    AXD    PUMPING-ENGINES. 


343 


Fig.   50.-TRIPI.K-EXFANS10N  Horizontal  Engine. 
(Worthington  Type,  steam-end  only.) 


PUMPING    AND    PUMPING-ENGINES. 


345 


^-'f 


Fig.  51. — Vertical  Compound  Pumi'Ing-engink. 
(Differential  Plunger  Type,  Smiih-Vaile.) 


PUMPING    AND    PUMPING-ENGINES.  347 

it  has  the  disadvantage  of  causing  the  L.-P.  cylinder  to  be 
less  accessible  for  adjustment  and  repairs,  and  makes  a  less 
rigid  construction.  It  is  not  often  employed  for  engines  of 
more  than  750^000  or  1,000,000  gals,  capacity,  and  is  not 
recommended  for  any.  In  vertical  engines,  either  compound 
or  triple-expansion,  the  steam-cylinders  may  be  tandem  (one 
above  the  other,  see  Fig.  51),  but  are  more  often  placed  side 
by  side ;  the  latter  arrangement  not  only  being  more  rigid,  but 
permitting  two  or  three  cranks  or  direct-acting  pump-cylinders 
to  be  used  and  thus  securing  a  more  continuous  flow. 

The  suction-lift  of  a  pump  may  be  made  25  or  26  feet, 
but  it  is  better  to  make  it  not  more  than  15  feet  if  possible. 
In  the  case  of  pumping  from  rivers  subject  to  great  variations 
in  height,  the  pump  must  be  raised  and  lowered  to  suit  the 
stages  of  the  river;  or,  better,  it  should  be  placed  in  a  water- 
tight pit  which  extends  above  the  highest  water.  This  con- 
struction is  necessary  on  the  Ohio  and  other  rivers  of  our 
**  central  basin."  In  the  new  Cincinnati  Water-works  re- 
cently constructed  the  pump-pit  is  95  feet  deep  and  98  feet 
in  diameter,  in  which  four  30,000,000-gallon  pumps  are  to  be 
placed  (see  Fig.  52). 

Pumps  in  such  a  pit  may  be  vertical,  direct-acting,  or 
crank-and-fly-wheel;  or  they  may  be  power-pumps,  the 
engine  being  upon  the  surface  and  thus  more  accessible.  An 
excellent  illustration  of  the  latter  arrangement  is  afforded  by 
the  Rockford,  111.,  plant,  recently  completed.  In  this  the 
pump  is  placed  79  feet  below  the  engine,  to  render  available 
a  large  flow  of  ground-water.  The  pumps  are  centrifugal, 
3.5  feet  diameter,  designed  for  300  to  350  revolutions  per 
minute  and  one  million  gallons  per  day  each,  with  a  suction- 
lift  of  26  feet  and  discharge  head  of  60  feet.  They  are 
driven  by  rope  transmission  from  vertical  compound  con- 
densing-engines  of  a  mechanical  efficiency  of  about  93^;  the 
plant  showing  a  duty  of  58,000,000  per  1000  lbs.  of  dry  steam. 


348 


IV A  TER-SUPPL  Y  ENGINEERING. 


I  Ahouf  ElMo 


\    ;    t\  /PiareiirJufi^llaltrooT^baclr. 

idi^ib- 9S/0'     T--">t   jTop Coping  El.  78. S(f 

fct— i^~»         _._  /  ...  "'  ^Top/ill. Sirnoo 


SJ&SJ* 


Brass  Nozzie. 


VerTicoii  Section  on  Tunnel  Axis. 


itorteontal  Section  on  Tunnel  Axis. 

Fig.  52. — PuMP-riT,  Cincinnati  Water-works. 


PUMPJXG   AND    PUMPING-ENGINES. 


349 


When  water  is  to  be  taken  from  a  deep  driven  well  the 
entire  pump  must  be  of  such  size  as  can  be  lowered  into  the 
tube,  and  those  at  present  in  use  are  driven  by  a  long  pump- 


SedTon    of    Shaft    Showincf 
/rrongement    of     Pumps. 


MItttinf 
Tunnel  19 

mis 

Vertical  Section  of  Sharft. 


Fig.  53. — Centrifugal-pump  Plant,  Rockford,  III. 

rod  extending  to  the  surface.  In  general  the  pump  is  single- 
acting,  its  cylinder  made  of  brass  tubing,  the  principle  being 
that   shown   in    Fig.   45,    page   323.     The  water-cylinder  is 


350  WATER-SUPPLY  ENGINEERING. 

suspended  from  a  drop-pipe  of  slightly  larger  diameter,  or  is 
locked  into  the  well-casing,  which  acts  as  a  discharge-pipe. 
The  steam-cylinder  is  placed  above  the  well-opening,  and  the 
engine  is  direct-acting  (see  Plate  XVII,  page  397).  The 
strain  on  the  pump-rod  should  always  be  tensile,  owing  to  its 
great  length;  hence,  to  render  this  pump  continuous  in  flow 
two  water-cylinders  are  furnished  with  independent  piston- 
rods.  The  great  weight  of  the  rod  and  column  of  water 
above  the  cylinder  in  a  deep  well  renders  great  velocity  of 
motion  impossible. 

If  the  pumping-engine  is  direct-acting,  it  is  evident  that 
any  repairs  to  or  inspection  of  the  pump  are  possible  only 
after  removing  the  engine  and  drawing  the  pump-rod  and 
cylinder  out  of  the  well.  To  facilitate  this  operation  a  work- 
ing-head is  often  employed ;  the  greater  advantage  in  its  use, 
however,  being  the  higher  efficiency  attainable.  The  work- 
ing-head is  a  contrivance  for  utilizing  the  power  of  an 
ordinary  slide-valve  engine,  converting  rotary  into  reciprocat- 
ing motion,  and  may  be  driven  by  belt  or  gearing.  The 
working-head  is  placed  over  the  well  and  drives  the  pump- 
rod;  the  engine  is  placed  at  a  greater  or  less  distance  away 
from  the  well.  A  modification  of  this  gives  a  more  nearly 
continuous  flow  to  either  single-  or  double-cylinder  pumps 
by  making  the  down-stroke  much  more  rapid  than  the  up. 

A  pump  has  recently  been  introduced  which  utilizes  the 
principle  of  the  screw  to  obtain  continuous  flow.  It  consists 
of  a  central  torsion-shaft,  on  which  a  pair  of  "runners"  is 
placed  every  3  to  5  feet.  The  runners  are  shaped  similar  to 
the  propellers  of  a  vessel,  and  fit  closely  to  the  sides  of  the 
well-casing.  A  lift  of  over  200  feet  has  been  made  with  such 
a  pump.      Its  efficiency  is  not  known. 

Every  pumping-engine  should  be  protected  by  a  building 
from  rust-producing  moisture,  from  dust  and  dirt,  and  from 
curious  or  malicious  tampering  with.      To  keep  from  it  dust 


PUMPING   Am    PUMPING-ENGINES.  35 1 

and  grit  from  the  coal-house  and  boiler-room  these  should  be 
entirely  separated  from  the  pumping-engine,  which  should 
have  a  room  entirely  to  itself.  Near  it  should  be  placed 
gauges  showing  steam-pressure  in  the  boilers,  pressure  in  the 
discharge-pipe,  and  vacuum  in  the  suction.  Also  a  counter, 
registering  the  number  of  revolutions  or  strokes  of  the  engine. 
The  foundation  of  the  pump  should  be  perfectly  rigid  and 
unyielding,  resting  upon  a  firm  soil,  and  substantial  and 
strong  to  resist  vibrations. 

The  pump-room  should  be  light,  dry,  and  easily  venti- 
lated; and  the  pump  readily  accessible  in  all  its  parts.  The 
boiler-room  should  be  close  to  the  pump-room,  that  the 
length  of  steam-piping  and  consequent  loss  of  heat  may  be 
as  small  as  possible.  The  boilers  should  always  be  of  such 
number  and  capacity  that  any  one  can  be  put  out  of  service 
without  rendering  impossible  the  maximum  work  at  any  time 
desirable.  They  should  be  placed  as  near  each  other  as 
possible  to  reduce  loss  of  heat  by  radiation.  The  steam- 
piping  should  be  so  arranged  that  any  boiler  may  be  used  for 
any  engine.  The  coal-house  should  be  as  near  the  fire-doors 
as  possible,  to  reduce  the  handling  of  coal.  A  good  plan  is 
to  place  a  long  coal-room  just  in  front  of  the  boilers,  with 
only  sufficient  room  between  to  permit  of  using  the  rake,  flue- 
cleaners,  and  other  boiler  tools.  The  boiler-room  should  be 
well  built-in  to  prevent  unnecessary  radiation  of  heat  in 
winter.  Boilers  have  been  known  to  have  their  efficiency 
decreased  5^  or  more  by  cold  weather.  Facilities  for  deliver- 
ing coal  to  the  station  should  not  be  neglected.  It  should 
be  near  a  railroad,  canal,  or  navigable  river  if  possible.  If 
the  coal  come  by  rail  it  may  be  economical  to  furnish  a  siding 
into  the  coal-room  or  along  its  outer  side;  and  if  by  water, 
to  provide  a  dock  and  hoisting-derrick  for  filling  the  bins. 


352  water-supply  engineering, 

Art.  85.     Boiler-tlants. 

Boilers  in  common  use  in  water- works  plants  may  be  clas- 
sified as  water-tube,  and  fire-tube  or  flue.  In  the  former  the 
water  passes  through  several  connected  tubes  so  arranged  that 
a  large  number  of  these  are  contained  inside  a  single  casing,  the 
fire  passing  through  the  casing  and  around  the  tubes.  In 
horizontal  return-tubular  (flue)  boilers  the  water  is  contained 
in  the  casing,  and  the  heated  air  passes  under  this  and  back 
through  the  tubes,  which  extend  through  the  boiler  from  end 
to  end  and  are  not  connected  with  each  other.  Flue  boilers 
other  than  horizontal  return-tubular  are  seldom  used  in  water- 
works. 

The  capacity  of  a  boiler  is  expressed  in  horse-powers. 
Theoretically  this  is  the  amount  of  work,  in  H.P.,  which  an 
engine  fed  by  this  boiler  could  perform  if  its  ef^ciency  were 
lOO^;  but  boilers  are  commercially  designated  by  arbitrary 
standards  of  capacity.  Fifteen  square  feet  of  heating-surface 
is  considered  equivalent  to  one  H.P.,  and  the  grate-area  is 
generally  about  -^-^  the  heating-surface.  On  page  353  are  shown 
the  average  dimensions  of  ordinary  return-tubular  boilers. 
In  the  Louisville  test  above  described  the  heating-surface 
was  but  7  square  feet  per  H.P.  developed  in  the  engine;  but 
if  only  70  million  duty  had  been  developed,  the  ratio  would 
have  been  about  15  square  feet. 

In  a  flue-boiler  the  boiler-shell  must  be  sufficiently  strong 
to  resist  the  maximum  steam-pressure.  In  a  water-tube 
boiler  only  the  tubes  and  steam-drum  must  resist  this 
pressure,  the  shell  serving  to  confine  the  heat  to  them.  For 
this  reason,  largely,  water-tube  boilers  are  frequently  used  for 
high  steam-pressures.  In  the  latter  boiler  the  scale,  being 
inside  the  tubes,  is  difficult  to  remove;  while  in  the  fire-tube 
boilers  the  removal  of  soot  and  other  fine  deposits  from  the 
flues  is  similarly  difficult. 


PUMPING   AND    FUMPiNG-ENGINES. 
b' 

IIe 


.    .  GROUND  PLAN 

front  elevation 

Fig.  54. — Setting  of  Return-tubular  Boiler. 

measurements  for  setting  tubular  boilers. 


Reference  Letters  on  Diagrams. 

No. 

A 

B 

c 

jD 

E 

F 

G 

// 

/ 

y 

K 

L 

i1/ 

Feet. 

Ins. 

Ins. 

Ins. 

Ins. 

Ins. 

Ins. 

Ins. 

Ins. 

Ins. 

Ins. 

Ins. 

Ins. 

I 

7 

30 

12 

20 

16 

45 

44 

7 

30 

62 

8s 

26 

19 

2 

8 

3f 

12 

20 

16 

48 

47 

8 

30 

68 

92 

26 

22 

3 

10 

42 

14 

20 

16 

48 

47 

8 

42 

74 

98 

27 

21 

♦ 

12 

44 

14 

24 

16 

48 

46^ 

10 

44 

76 

100 

27 

21 

5 

M 

48 

16 

24 

16 

47 

4SV^ 

10 

48 

88 

lo"! 

26 

21 

6 

12 

60 

18 

24 

20 

50 

48(4, 

12 

60 

108 

118 

26 

24 

7 

16 

60 

18 

26 

20 

50 

48 

12 

60 

108 

n8 

26 

24 

8 

16 

66 

18 

28 

20 

50 

48 

12 

66 

114 

124 

26 

24 

9 

18 

72 

20 

30 

20 

50 

48^, 

12 

72 

120 

130 

26 

24 

10 

18 

84 

20 

30 

20 

50 

48 

12 

84 

'32 

142 

26 

24 

Number  of 

No. 

N 

0 

p 

Q 

R 

5 

r 

U 

Number  of 

Common  Brick 

Ft.  Ins. 

Ins. 

Ins. 

Ins. 

Ins. 

Ins. 

Ins. 

Ins. 

Fire-brick. 

above  Floor- 

level. 

1 

II      6 

20 

40 

12 

16 

36 

34 

500 

4,800 

2 

12      6 

24 

40 

12 

16 

36 

34 

600 

6,000 

3 

14      8 

28 

46 

12 

16 

42 

42 

750 

8,000 

4 

17      0 

32 

52 

12 

16 

48 

49 

900 

10.400 

S 

19         2 

36 

5« 

12 

20 

S4 

84 

1 000 

13,800 

6 

17       10 

32 

50 

16 

24 

48 

49 

1300 

17,000 

T 

22          0 

40 

.Sb 

16 

24 

54 

96 

1400 

21,000 

8 

22           2 

40 

,sfc 

16 

24 

54 

96 

>550 

23,000 

9 

24        6 

40 

62 

16 

24 

60 

108 

1800 

26,500 

10 

24       6 

40 

62 

16 

24 

60 

108 

2000 

31,000 

354  WArER-SUPPLY  ENGINEERING. 

The  matter  of  height  and  area  of  chimneys  has  not  been 
reduced  to  an  exact  science,  and  in  a  large  number  of  cases 
is  fixed  by  guesswork.  The  empirical  formula  of  Abendroth 
&  Root,  which  is  perhaps  as  satisfactory  as  any,  is 

20I 


\^li  -  8' 

in  which  c  is  the  area  of  the  chimney  in  square  inches  per 
square  foot  of  grate-surface,  and  h  is  the  height  of  the 
chimney  above  the  grate.  The  height  of  chimney  depends 
upon  the  draught  desired.  Anthracite  screenings  probably 
require  the  most  draught,  and  wood  the  least.  Probably  no 
chimney  should  be  less  than  40  feet  in  height,  and  the  higher 
it  is  the  greater  the  draught  which  can  be  obtained;  although 
this  is  dependent  also  upon  the  force  and  direction  of  wind, 
the  outside  temperature,  and  that  of  the  air  in  the  chimney. 
Chimneys  have  been  built  over  200  feet  in  height,  but  prob- 
ably 75  to  125  are  the  ordinary  limits  of  chimneys  for  water- 
works plants. 

Art.  8G.     Other  Motive  Powers  for  Pumps. 

Next  to  steam,  hydraulic  power  has  probably  been  used 
more  than  any  other  for  driving  pumps.  The  near  future 
may,  however,  and  probably  will,  see  electricity  used  quite 
widely  for  small  plants,  and  perhaps  for  large  ones  under 
some  conditions.  In  some  cases  gas-,  gasoline-,  oil-,  hot-air-, 
and  wind-engines  are  used  for  small  plants.  (The  use  of  oil 
or  gas  under  steam-boilers  is  of  course  but  a  detail  of  a 
steam-plant.) 

Hydraulic  power  is  conveniently  used  where  water  is 
taken  from  a  river  whose  dry-weather  flow  sufficiently  exceeds 
the  amount  to  be  pumped  and  which  can  be  dammed  at  this 
point.      Philadelphia's  Schuylkill  supply  was  for  years  wholly, 


PUMPING   AND    PUMPING-ENGINES.  355 

and  is  still  partly,  pumped   in  this  way.      The  motive  power 

is  the  ordinary  water-motor,  generally  a  high-grade  turbine. 

The    rotary    motion    of   the    turbine    may    be   communicated 

directly  to  a  rotary  pump,  or  by  crank-shaft  to  a  reciprocating 

pump.      The   pump   and    turbine    should    generally    be    near 

together,  and   the   head-race  of  one   may  serve   to   feed   the 

other  also.      A   turbine  with  an  efificiency  of  .80  may  readily 

be    obtained,    and,    given    a    pumping-engine    with    a    94^ 

efificiency  upon  the  same  shaft,   the  total  efificiency  will  be 

about    75/^.      If   gearing    is   employed    between    turbine   and 

pump,  the  efificiency  may  be  reduced  to  60^.      Assuming  an 

efificiency  of  .70,  the  proportion  of  total  flow  which  can   be 

.70// 

pumped  is  - — ■ -^  in  which  H  is  the  available  head  in  the 

^       ^  Jl  -\-  .70// 

river  and  //  is  the  total  head  against  which  the  pumps  must 
work.  This  method  of  furnishing  power  for  water-supplies  is 
subject  to  intermission  by  droughts  in  a  majority  of  cities 
where  it  is  possible  at  all,  and  in  such  cases  an  auxiliary 
steam-plant  or  other  ever-available  source  of  power  should  be 
provided  for  occasional  use. 

It  sometimes  happens  that  different  parts  of  a  city  lie  at 
such  greatly  different  elevations  that  to  furnish  water  to  all 
through  the  same  pipe  system  would  necessitate  providing  a 
very  low  pressure  in  the  higher  part  or  an  excessive  one  in 
the  lower  part  of  the  city;  and  to  avoid  this  two  distribution 
systems  are  furnished,  with  a  reservoir  for  each,  or  a  stand- 
pipe  taking  the  place  of  the  upper  reservoir.  The  mainte- 
nance of  separate  pumping-mains  would  be  expensive,  as 
would  that  of  a  separate  pumping-station  at  the  low-service 
reservoir.  This  difficulty  has  been  met  in  some  plants  by 
placing  a  hydraulic  motor  on  the  pumping-main  to  the  low- 
service  reservoir,  which  motor  is  run  by  the  water  on  its  way 
to  this  reservoir.  At  Burlington,  Vt.,  a  motor  5  to  10  feet 
below    the    water-surface     in    a    low-service    reservoir    raises 


356  WATER-SUPPLY   ENGINEERING. 

water  60  feet  to  a  high-service  reservoir.  If  the  eflficiency  of 
this  motor  were  .90,  it  could  lift  .15  to  .075  of  the  water 
flowing  through  it. 

Such  a  motor  may  be  of  the  general  form  of  a  reciprocat- 
ing steam-pump;  or  some  form  of  ram  may  be  employed. 
The  older  style  of  ram  was  capable  of  an  efificiency  of  about 
65  to  70  per  cent  under  practical  conditions.  Recent  im- 
provements are  said  to  bring  this  up  to  82^.  Electric  motors 
are  used  in  a  number  of  small  water-plants,  the  current  being 
generally  purchased  from  an  electric-power  company.  The 
power  is  transmitted  from  the  motor  either  by  gearing  on  the 
motor-shaft  or  by  belt;  the  latter  being  generally  preferable. 
The  efficiency  of  the  combined  plant — steam-engine,  line, 
and  dynamo — may  easily  be  60  to  65  per  cent.  If  the  engine 
and  boiler  have  a  duty  of  100,000,000  foot-pounds — which, 
being  of  considerable  power,  it  may  easily  have — the  efficiency 
of  the  two  plants  combined  would  be  60  to  65  million  foot- 
pounds; a  greater  efficiency  than  a  small  pumping-plant  could 
expect  to  attain,  but  less  than  a  large  one  should  be  designed 
for.  Under  these  conditions  a  number  of  small  pumps  run 
from  a  central  steam-plant,  or  one  such  pump  fiom  a  general 
electric-power  plant,  would  be  an  economical  arrangement. 
In  connection  with  this  comparison  it  should  be  remembered 
that  such  a  plant  will  require  no  more  space  than  a  steam 
pumping-engine  alone,  no  boiler-  or  coal-room  being  required. 
A  saving  may  thus  be  made  in  the  building,  and  in  super- 
intendence also — the  latter  a  considerable  item  in  many  cases. 
It  may  also  be  that  a  cheaper  source  of  power — as  a  hydraulic 
plant — or  a  saving  in  the  hauling  of  coal  will  render  economi- 
cal the  separation  of  engine  and  pump  by  a  considerable 
distance  and  electrical  transmission  rf  power  between  the  two. 
One  of  the  largest  electric  pumping-plants  in  the  country  is 
at  San  Antonio,  Tex.,  where  a  2-million-gallon  pump  is  run 


PUMPING   AND    P U M PING-ENG INES.  357 

by  a  30-H.P.  motor  with  electricity  furnished  by  the  city 
electric-light  plant. 

Gas-,  gasoline-,  and  oil-engines  have  been  used  in  a 
number  of  small  plants,  but  are  not  economical  for  large  ones. 
The  economy  over  steam  lies  in  the  smaller  first  cost  of 
engine  and  building,  the  small  expense  for  running  and  main- 
tenance, and  the  ability  to  run  for  a  few  hours  a  day  only 
without  Avaste  of  fuel.  One  oil-engine  in  a  certain  small 
plant  is  started  by  a  plumber  each  morning,  visited  at  noon, 
and  stopped  at  night,  the  plumber  receiving  $350  per  year 
for  his  services.  At  Midvale,  N.  J.,  a  triplex  pump  lifting 
65  feet  is  run  by  a  4-H.P.  engine  on  0.312  gals,  of  gasoline 
per  H.P.  per  hour.  At  Greensburg,  Ind.,  a  triplex  pump, 
lift  81.3  feet,  is  run  by  a  6-H.P.  engine  on  0.47  gals,  of 
crude  oil  per  H.P.  hour.  At  Winchester,  Mass.,  a  triplex 
pump,  500,000  gals,  capacity,  143  feet  lift,  is  run  by  a 
20-H.P.  Hornsby-Akroyd  oil-engine  on  0.17  gals,  of  oil 
(150°  test  kerosene)  per  H.P.  hour,  or  11,516,518  foot- 
pounds of  work  per  gallon  of  oil. 

Preeman  C.  Coffin  considers  that  the  table  on  page  358 
gives  a  fair  comparison  of  the  total  annual  costs  of  pumping 
with  different  types  of  engines;  this  estimate  including  sup- 
plies, repairs,  attendance,  interest  on  cost,  and  depreciation 
(at  4  and  3  per  cent  respectively),  and  fuel. 

This  cost  will  of  course  vary  with  the  character  of  fuel 
and  efficiency  of  engine  of  each  kind,  and  this  table  can  only 
be  taken  as  an  approximation,  which  may  be  useful  in  pre- 
liminary study  of  what  is  desirable  for  a  given  small  plant. 

A  description  of  these  engines  and  their  advantages  are 
thus  briefly  summed  up  by  Mr.  Coffin  in  the  Journal  of  the 
N.  E.  W.  \V.  Assn.  for  March  1899: 

"  Gas-  and  gasoline-engines  are  practically  alike  in  con- 
struction and  operation;  the  same  engine  can  be  used  with 
either  fuel,  a  few  alterations  being  required  in  the  arrangement 


358 


WA  TER-SUPPL  V  ENGINEERING. 


when  the  fuel  is  changed.  The  oil-engine  is  similar  in  general 
appearance  and  operation,  but  the  treatment  of  the  fuel  in  the 
engine  differs  from  that  of  gasoline. 

TABLE    GIVING    COMPARATIVE    ANNUAL    COST    OF     PUMPING    WITH 
DIFFERENT    TYPES    OF    POWER. 

(Journal  N.  E.  W.  W.  Assn.) 


Average 

Oil-engine; 
Oil  at  gets, 
per  Gallon. 

Gasoline- 
engine; 
Gasoline  at 

9  cts.  per 
Gallon. 

Gas-engine. 

Steam-pump. 

Daily 
Pumping, 
in  Gallons. 

Gas  at  |i 
per  1000. 

Gas  at  $0. 50 
per  1000. 

Coal  at 

I5 
per  Ton. 

Coal  at 

$4 
per  Ton. 

Coal  at 

% 
per  Ton. 

50,000 
100,000 
200,000 
300,000 
400,000 
500,000 

%   770 
1275 
2200 
3085 
3920 
4745 

$  735 
1200 
2050 

2875 
3640 
4400 

%  920 
1580 
2815 
4000 
5140 
6270 

$   675 
1035 
1820 
2510 
3150 
3780 

$1230 
1740 
2525 
3130 
3700 
4200 

$1160 
1600 
2300 
2850 
3350 
3790 

$1090 
1460 
2075 
2570 
3000 
3380 

"  In  a  gas-engine  the  gas  is  introduced  into  the  cylinder 
and  mixed  with  air  which  is  drawn  through  a  valve  into  the 
cylinder  by  the  outward  stroke  of  the  piston,  the  mixture  is 
compressed  by  the  return  stroke  and  fired  by  an  electric 
spark  or  an  ignition-tube. 

"  The  cylinder  is  open  on  one  end.  The  explosion  of 
the  air  and  gas  behind  the  piston  drives  it  forward  and  imparts 
the  energy  to  the  fly-wheel,  which  is  very  heavy.  There  is 
but  one  explosion  in  two  complete  revolutions,  the  return  of 
the  piston  forcing  the  gases  formed  by  the  combustion  out 
at  the  exhaust,  the  next  forward  stroke  drawing  in  the  air 
and  admitting  the  gas,  and  the  return  stroke  completing  the 
cycle  of  work  and  compressing  the  charge  for  the  next  explo- 
sion. The  gasoline-engine  works  in  precisely  the  same  way, 
except  that  the  fuel  is  forced  in  by  a  pump  worked  by  the 
revolution  of  the  engine  and  is  turned  to  gas  within  the 
cylinder  or  combustion-chamber  before  mixing  with  the  air. 

"  The  principal  difference  in  the  working  of  the  oil-engine 
is  that  the  fuel,  not  being  as  volatile  as  gasoline,  is  introduced 


PUMPING   AND    PUMPING-ENGINES.  359 

in  a  fine  spray  to  a  vaporizer,  where  it  is  turned  into  vapor  by 
the  heated  walls  and  then  mixed  with  air.  The  vaporizer 
must  be  heated  by  a  special  lamp  before  starting  the  engine; 
this  requires  from  seven  to  ten  minutes,  and  therefore  the 
oil-engine  requires  that  much  more  time  to  start  it  than  the 
gas-  or  gasoline-engine,  which  simply  requires  the  supply-cock 
to  be  opened,  a  few  turns  to  be  given  to  the  fly-wheel  and  it 
is  off,  if  there  is  no  difficulty  with  the  battery  which  provides 
the  spark  for  firing.  This  seems  to  be  the  weak  point  in  the 
gas-engine;  at  least  the  only  difficulty  that  I  have  seen  in 
starting  and  running  them  seems  to  be  connected  in  some 
way  with  the  battery.  Some  of  the  oil-engines  require  no 
battery,  the  charge  being  ignited  after  the  engine  is  started 
by  the  heat  of  the  walls  of  the  vaporizer  in  combination  with 
the  pressure  produced  by  the  return  of  the  piston.  .  .  .  Per- 
haps the  most  important  feature  in  the  operation  of  internal- 
combustion  engines  is  the  attendance.  Any  one  with  ordinary 
intelligence  and  no  training  as  an  engineer  can  be  taught  in 
a  short  time  to  run  one.  In  a  well-designed  plant,  properly 
supplied  with  large  oil-cups,  the  necessary  attendance  is 
limited  to  starting  the  engine,  providing  a  sufficient  supply 
of  fuel  in  the  tank  and  oil  in  the  cups,  and  stopping  it  at  the 
proper  time.  Starting  under  ordinary  conditions  requires 
from  a  minimum  of  one  minute  with  gas-  or  gasoline-engines 
to  a  maximum  of  fifteen  with  oil-engines. 

"  The  speed  of  these  engines  seems  to  be  most  perfectly 
regulated  by  the  governor  which  controls  the  supply  of  fuel, 
a  sudden  variation  in  load  making  but  slight  change  in  speed. 
If  a  main  should  break  in  front  of  the  pump  the  speed  would 
hardly  vary  lo^.  On  the  other  hand,  there  is  very  little 
adjustment  of  speed  possible.  About  15^  from  the  rated 
speed  either  way  is  as  much  variation  as  can  be  obtained. 
If  a  pumping-plant  were  required  in  which  the  running 
capacity  could  be  reduced  50^^,  it  would  be  necessary  to  use 


360  WATER-SUPPLY  ENGINEERING. 

two  small  pumps,  one  each  side  of  the  engine,  with  friction- 
clutches,  when  either  or  both  pumps  could  be  run.  As  the 
engine  so  readily  adapts  itself  to  a  change  of  load,  a  pump 
could  be  thrown  on  or  off  at  any  time.  These  engines  run 
very  economically  with  a  small  load." 

For  very  small  plants  windmills  are  sometimes  used,  in 
connection  with  a  tank  for  storage  during  calm  weather.  It 
is  very  desirable,  however,  to  provide  a  gasoline-  or  similar 
engine  to  supplement  the  wind-engine.  The  whole  may  be 
combined  in  one  structure,  the  windmill  above  the  tank,  the 
gasoline-engine  housed  in  beneath  it.  Wind-engines  may  be 
obtained  of  40  H.P.  easily  capable  of  pumping  500,000  gals. 
per  day  100  feet  high;  but  dependence  probably  should  not 
be  placed  upon  an  average  of  more  than  200,000  gals,  per 
day  from  such  an  engine,  owing  to  the  uncertainty  of  the 
wind. 

Hot-air-engines  have  been  used  for  small  domestic  plants 
with  some  success,  but  not  for  village  or  city  plants  to 
the  author's  knowledge.  The  Diesel  Motor,  which  uses 
petroleum,  has  just  been  introduced  into  this  country  from 
Germany  and  is  said  to  give  a  thermal  efficiency  50^^  greater 
than  the  most  perfect  steam-engine;  but  this  has  not  yet  been 
demonstrated  by  use. 

A  contrivance  for  raising  water  called  the  "air-lift," 
which  is  not  strictly  a  pumping-machine,  has  been  brought 
into  practical  use  within  the  past  five  or  ten  years  and  gives 
excellent  service  under  certain  conditions.  Its  principle  of 
action  is  the  lessened  specific  gravity  of  water  in  which  air  is 
contained  in  considerable  quantity,  or  through  which  it  is 
rising  in  bubbles.  The  air-lift  consists  essentially  of  an  air- 
pump,  and  an  air-pipe  leading  from  this  to  the  bottom  of  a 
water-tube,  into  which  tube  air  is  discharged.  The  air,  rising 
into  and  through  the  water  in  the  tube,  causes  the  surface  of 
this  to  rise,  since  the  atmospheric  or  other  pressure  at  the 


PUMPING   AND    PUMPING-ENGINES. 


361 


base  remains  the  same.  By  forcing  in  sufficient  air  the  water 
and  air  combined  rise  to  the  top  of  the  tube  and  overflow. 
This  lift  has  shown  itself  particularly  adapted  to  increasing 
the  flow  from  deep  wells,  but  is  uneconomical  for  any  kind 
of  surface  pumping.  Different  manufacturers  vary  the  details 
somewhat, — some,  for  instance,  placing  the  air-tube  within 
and  others  without  the  water-tube  (see  Fig.  55). 

Little  accurate  scientific  knowledge  has  yet  been  obtained 
concerning  the  working  of  the  air-lift,  and  it  is  probable  that 
its  efficiency  will  be  increased  within  the  next  few  years. 
Efficiencies  of  from  2  to  50  per  cent  have  been  obtained 
from  air-compression  and  lift  combined.  Probably  25  to  28 
feet  is  the  maximum  height  to  which  the  water  can  be  raised 
with  any  success.  It  is  generally 
considered  necessary  to  immerse 
the  water-tube  one  to  one-and-a- 
half  times  as  deep  below  the 
ground-water  surface  as  is  the 
desired  lift  above  it.  Some  tests 
have  seemed  to  indicate  better 
results  from  such  an  arrangement 
as  /;,  Fig.  55,  than  from  a;  the 
air-pipe  in  b  being  simply  lowered 
into  the  well-casing,  12  to  18 
inches  of  its  lower  end  being  per- 
forated with  a  large  number  of  fig.  55.— Air-lift  Pumps. 
holes.  One  of  the  chief  advantages  of  the  air-lift  is  the  flow 
attainable  by  it  from  small  wells,  as  compared  with  a  deep- 
well  pump.  With  a  double-acting  or  continuous-flow  deep- 
well  pump  probably  the  greatest  flow  obtainable  is  120,000 
gals,  per  day  from  a  6-inch  and  350,000  from  a  lo-inch  tube- 
well;  while  from  a  lO-inch  well  at  Indianapolis  an  air-lift 
pump  raised  about  1,500,000  gals,  per  day  to  a  height  of 
25.7  to  27.3   feet.      If  the  tube  had  been  18  or  20  inches  in 


362  WATER-SUPPLY  ENGINEERING. 

diameter  for  30  feet  below  the  surface,  however,  a  deep-well 
pump  of  the  same  capacity  could  have  been  used.  An 
advantage  of  the  air-lift  pump  is  that  the  moving  parts  are 
all  above  ground  and  such  as  to  require  little  attention ;  and 
the  pipe  below  the  surface  needs  little  or  no  attention  and 
can  easily  be  removed  if  necessary. 

The  air-lift  is  most  useful  where  the  quantity  of  water  is 
the  chief  concern,  and  the  first  cost  is  of  more  importance 
than  the  cost  of  operation.  It  is  the  best  pumping  appliance 
on  the  market  for  obtaining  a  large  quantity  of  water  from  a 
small  hole.  The  facility  with  which  an  air-lift  plant  can  be 
applied  to  a  well  and  altered  as  to  depth  of  air-pipe  and  other 
conditions,  and  its  freedom  from  injury  or  wear  by  muddy  or 
gritty  water,  causes  it  to  be  especially  adapted  to  testing  the 
flow  of  deep  wells. 

As  in  the  case  of  steam-pumps,  air-lifts — the  chief  details 
of  which  are  patented — are  generally  put  in  by  contract.  This 
should  stipulate  not  only  the  delivery  per  day,  but  the 
efficiency  of  the  entire  plant.  Probably  5  or  6  per  cent 
thermal  efficiency  is  the  greatest  which  can  be  obtained  by 
present  methods;  or  25  to  35  percent  mechanical  efficiency 
for  combined  air-compressor  and  lift. 

QUERIES. 

27.  A  direct-acting  pump  has  a  water-cylinder  and  piston  18 
inches  diameter,  a  steam-cylinder  and  piston  14  inches  diameter. 
From  it  a  12-inch  pumping-main  one  mile  long  leads  to  a  reservoir 
150  feet  elevation  above  the  pump  ;  and  a  16-inch  suction-pipe  con- 
nects the  pump  with  the  water  in  the  suction-well,  which  is  100  feet 
distant  from  and  at  an  elevation  25  feet  lower  than  the  pump.  If  the 
efficiency  of  the  pumping-engine  is  90^^,  what  pressure  of  steam, must 
be  exerted  on  the  steam-piston  to  start  pumping  at  the  rate  of  two 
million  gallons  per  day  ?  the  pump  attaining  this  rate  from  a  state  of 
rest  in  one  minute.  New  cast-iron  pipe  ;  no  valves  or  other  obstruc- 
tions ;  mains  filled  with  water. 

28.  From  the  table  on  page  332,  records  of  the  sixth  day,  find 


PUMPING   AND    PUMPING-ENGINES.  363 

the  amount  of  ash  in  the  coal  ;  the  amount  of  dry  steam  created  by 
one  pound  of  coal  ;  and  the  percentage  of  water  in  the  steam.  How 
many  thermal  units  did  a  pound  of  dry  steam  contain  on  each  of  the 
six  days  ? 

29.  Suggest  other  methods  than  those  mentioned  in  Art.  83  for 
utilizing  more  of  the  heat  obtained  from  the  coal  burned  under  a 
boiler. 

30.  Referring  to  the  table  on  page  339,  from  (44)  and  (45) 
determine  the  average  heat  of  the  feed-water,  the  temperature  of 
steam  in  the  boiler  being  365°. 


CHAPTER    XV. 

DESIGNING. 

Art.  87.     Collecting  the  Data. 

The  problem  presented  to  the  designing  engineer  is 
generally:  Given  a  certain  city  to  be  supplied  or  territory  to 
be  irrigated ;  to  decide  upon  a  source  of  supply  which  will 
meet  the  requirements  as  to  both  quality  and  quantity,  to 
properly  develop  this  source,  conduct  the  water  to  the  point 
of  utilization,  and  arrange  for  its  distribution  to  meet  the 
various  requirements  demanded  of  the  system. 

If  a  city  supply  is  to  be  obtained,  the  first  problem  pre- 
sented is  the  population  to  be  provided  for;  and  the  solving 
of  this  requires  that  all  past  records  of  population  be  obtained. 
These  can  generally  be  furnished  by  the  city  officers  or 
gleaned  from  reports  of  the  Boards  of  Health,  School,  and 
Police,  and  State  and  U.  S.  census  reports. 

A  map  of  the  city  should  be  obtained  showing  curb  as 
well  as  property  lines,  and  the  location  as  far  as  possible  of 
all  underground  structures  within  the  street  limits,  gas-pipes, 
fire-wells,  subcellars  or  vaults,  etc.  A  convenient  scale  for 
such  map  is  200  feet  to  i  inch,  but  if  the  size  of  the  city  is 
such  that  this  scale  would  necessitate  the  use  of  paper  more 
than  3  feet  wide  it  may  be  better  to  use  a  scale  of  250  or 
even  300  feet  to  i  inch.  It  is  inadvjsable  to  use  a  smaller 
scale  than  this,  and  if  the  resulting  map  is  still  too  large  for 
the  paper  it  may  be  necessary  to  spread  it  over  two  or  more 

364 


DESIGNING.  36  f 

sheets,  when  the  use  of  the  200-foot  scale  is  advisable. 
Extreme  accuracy  in  this  map  is  not  necessary  for  the  plan- 
ning of  the  system,  but  for  preparing  the  estimate  of  cost  it 
is  desirable  that  the  lengths  of  pipe  may  be  scaled  from  the 
map  with  tolerable  accuracy.  It  is  advisable  to  limit  the 
possible  error  in  lineal  dimensions  to  0.5  per  cent. 

A  topographical  survey  of  the  city  can  be  used  to  advan- 
tage, but  the  benefits  accruing  do  not  ordinarily  warrant 
incurring  the  expense  for  this  purpose  alone ;  and  a  few  levels 
taken  at  the  lowest  and  highest  points  of  each  section  of  the 
city  will  generally  be  sufficient. 

The  problem  of  fixing  upon  the  source  of  supply  generally 
involves  the  comparative  consideration  of  all  possible  sources. 
The  water  of  streams  or  lakes  should  be  submitted  to  a 
chemist  and  bacteriologist  for  examination,  as  should  samples 
of  water  from  test-wells  if  there  is  a  probability  of  using 
ground-water.  The  banks  of  streams  and  lakes,  and  of  their 
tributaries,  should  be  examined  for  sewers,  drains,  out- 
houses, slaughter-houses,  or  other  sources  of  pollution.  If  a 
surface  supply  is  in  question,  the  best  location  for  the  reser- 
voir will  require  a  survey  of  the  limiting  line  of  the  catchment 
area;  a  line  of  levels  along  the  valley  giving  elevations 
relative  to  the  city;  test-borings  at  proposed  reservoir-sites 
to  determine  the  character  of  foundation  obtainable;  and  an 
accurate  topographical  survey  of  the  dam-site  and  of  the 
reservoir-location  above  it,  that  for  the  dam  generally  locating 
I-  to  5-foot  contours,  while  5-  to  25-foot  contours  may  be 
sufficient  for  the  reservoir-site.  A  few  test-pits  should  be 
dug  in  the  reservoir-site  to  determine  the  depth  reached  by 
organic  matter  in  the  soil;  and  the  location  of  all  swamps, 
ponds,  stables  or  cow-houses,  buildings,  roads,  and  other 
natural  and  artificial  features  should  be  determined.  It  will 
be  necessary  also  to  learn  who  are  the  owners  of  the  property 
in  question,  and  in  fact  of  all  which  is  in  the  catchment-bnsi'i. 


366  WATER-SUPPLY  ENGINEERING. 

If  ground-water  is  considered,  the  geology  of  the  sur- 
rounding country  should  be  carefully  studied  and  the  location 
and  history  of  all  wells  in  the  neighborhood — their  depth, 
character  of  strata  which  they  pierce,  and  quantity  and  quality 
of  flow  from  year  to  year.  If  the  upper  outcrop  of  the 
water-bearing  stratum  is  within  25  or  30  miles,  especially  if 
the  formation  be  glacial,  the  probability  of  contaminated 
water  entering  it  should  be  investigated. 

If  the  supply  be  from  a  storage-reservoir,  the  best  conduit 
line  between  this  and  the  city  should  be  determined  by 
survey.  If  an  open  conduit  be  employed,  the  survey  will 
assume  much  the  character  of  a  railroad  survey  for  a  road 
with  its  grade  and  terminals  fixed. 

The  location  of  pumping-station,  standpipe,  distributing- 
reservoir,  and  some  other  features  of  the  system  will  call  for 
special  investigations  and  surveys,  the  latter  mainly  consisting 
of  measurements  of  the  distances  and  relative  elevations 
between  these  and  the  city. 

Estimation  of  the  quantity  of  water  flowing  in  rivers  is 
made  by  obtaining  with  either  floats  or  current-meter  the 
velocity  in  a  cross-section  whose  area  has  been  measured  (see 
Art.  65,  (63)).  The  measurement  may  be  taken  with  a 
graduated  rod  if  the  water  be  nowhere  more  than  8  or  10 
feet  deep,  or  with  a  plumb-line  if  deeper  than  this.  The 
best  rod  for  the  purpose  is  a  round  one  about  2  inches 
in  diameter  throughout,  weighted  at  the  lower  end,  and 
graduated  to  feet  and  tenths.  The  plumb-line  should  be 
braided  of  linen  or  silk,  and  graduated  after  having  been 
soaked,  and  while  suspended  with  the  plumb  immersed  in 
water.  The  boat  should,  while  measurements  are  being 
taken,  be  kept  in  line  between  range-poles  on  the  opposite 
banks  on  the  line  of  cross-section  (which  should  be  normal  to 
the  stream-flow),  and  the  location  of  the  boat  determined  by 
triangulation   from   two   transits   in  known  positions,   angles 


DESIGNING.  367 

being  taken  by  each  simultaneously  with  the  soundings. 
The  depths  obtained  are  referred  to  the  water-surface,  whose 
elevation  is  known. 

The  yield  of  a  small  stream  may  be  obtained  by  use  of  a 
weir  (see  Art.  65);  that  of  an  artesian  well,  by  catching  the 
flow  in  casks  of  known  capacity,  and  noting  the  number  of 
times  they  are  filled  in  a  given  period,  or  by  receiving  the 
flow  in  a  flume  and  measuring  it  by  a  weir.  The  natural  flow 
of  wells  is  generally  increased,  both  during  the  test  and  for 
practical  use,  by  a  pump,  either  surface,  deep-well,  or  air-lift. 

The  test  of  wells  should  extend  over  at  least  a  week,  with 
several  gaugings  daily,  if  an  estimate  at  all  accurate  is  desired; 
and  tests  are  sometimes  continued  for  a  month  or  more. 
River  gaugings  should  be  made  during  the  lowest  water  if 
possible,  and  compared  with  calculations  of  the  probable 
minimum  yield  to  be  expected  from  the  drainage  area. 
Gaugings  of  certain  rivers  extending  over  long  periods  of  time 
can  be  obtained  from  government  reports  or  the  records  of 
water-power  companies,  canals,  or  others;  but  such  rivers  are 
unfortunately  few. 

All  obtainable  rainfall  data  should  be  collected;  and  one 
or  more  rain-gauges  should  be  established  in  the  catchment 
areas  under  consideration  as  soon  as  the  investigation  is 
begun,  and  maintained  throughout  the  time  of  the  investiga- 
tion, designing,  and  construction;  and  it  will  be  desirable  to 
continue  their  use  on  the  watershed  adopted,  after  the  plant 
is  in  service. 

The  above  applies  largely  to  irrigation  systems  also.  But 
the  quality  of  supply  does  not  demand  such  careful  investiga- 
tion, and  the  quantity  depends  upon  the  area  to  be  irrigated 
rather  than  population.  In  most  cases  the  aim  is  to  obtain 
all  the  water  possible,  more  land  than  it  will  irrigate  being 
generally  available  for  farms. 


368  water-supply  engineering. 

Art.  88.     Selecting  the  Supply. 

If  the  city  is  upon  or  near  a  river  or  lake,  this  forms  the 
most  obvious  source  of  supply.  Unfortunately  there  are  few 
in  the  settled  parts  of  the  country  which  are  not  more  or  less 
polluted;  and  there  is  a  probability  that  settlements  will 
before  long  be  established  along  the  rivers  in  sections  not 
now  populated.  Many  cities  which  originally  drew  their 
supply  from  their  own  river-fronts  have  been  forced  to 
abandon  this  supply  on  account  of  the  fatal  epidemics  of 
disease  clearly  traceable  to  it;  and  many  others  are  eagerly 
searching  for  purer  supplies  for  the  same  reason.  A  clearer 
foresight  and  shrewder  economy  would  in  many  cases  have 
led  to  the  acquiring  of  drainage-basins  and  reservoir-sites 
when  they  could  have  been  obtained  at  a  much  lower  cost 
than  must  now  be  paid  for  them.  Whatever  the  opinions  of 
the  citizens,  it  would  seem  to  be  the  engineer's  duty  to  place 
the  river  as  the  last  rather  than  the  first  alternative  source, 
and  to  plainly  and  forcibly  state  to  the  public  his  reasons 
therefor.  If  river-water  is  to  be  used,  purification,  either 
immediate  or  in  the  future,  should  be  provided  for. 

The  present  quality  of  a  river  supply  may  be  learned 
approximately  by  chemical  and  bacterial  analyses,  in  connec- 
tion with  a  searching  investigation  for  all  causes  of  contamina- 
tion (Chapters  II  and  VII).  It  is  desirable  to  obtain  analyses 
not  only  during  ordinary  periods  of  flow,  but  during  low  and 
high  water  also.  In  determining  the  quantity  of  flow  in  a 
river  it  must  be  remembered  that  low  water  generally  lasts 
for  several  days  or  weeks,  while  the  maximum  rate  generally 
continues  but  a  few  hours.  If  no  storage  is  to  be  supplied, 
particular  care  must  be  taken  to  learn  the  very  lowest  rate  of 
flow  attained  by  the  river,  and  a  margin  of  safety  should  be 
used  in  connection  with  this. 

In  testing  the  quality  of  a  ground-water,  analyses  should 


DESIGNING.  369 

be  taken  during  the  quantity  test;  and  particularly  at  the 
end  of  this,  since  the  quality  often  changes  as  the  flow  con- 
tinues, owing  to  differences  in  the  composition  of  the  near 
and  distant  parts  of  the  water-yielding  stratum. 

Before  or  while  making  exhaustive  tests  of  the  quality 
and  quantity  of  water  available  from  different  sources,  an 
estimate  of  that  required  should  be  prepared.  The  estimate 
of  population  can  be  approximated  as  suggested  in  Art.  12; 
a  considerable  extra  allowance  for  growth  being  made  for 
small  cities.  The  decision  as  to  quantity  of  consumption  per 
capita  is  a  most  difficult  one.  If  meters  are  to  be  used,  and 
every  effort  made  to  keep  the  consumption  within  reasonable 
limits,  60  gals,  for  residential  and  80  to  100  for  factory  towns 
should  be  sufficient.  If  no  efforts  in  this  direction  are  made, 
however,  the  consumption  may  reach  any  figure  short  of  a 
thousand  gallons  per  capita,  and  the  only  logical  conclusion 
would  be  to  furnish  all  the  water  available. 

In  case  a  water-supply  of  good  quality  can  be  obtained  in 
sufficient  quantity  for  domestic  consumption  only,  but  water 
of  a  more  polluted  supply  from  a  river  is  also  available,  the 
latter  may  be  used  for  an  auxiliary  supply  for  factories, 
street-  and  sewer-cleaning,  public  fountains,  and  similar  pur- 
poses; although  great  care  should  be  taken  that  it  be 
excluded  from  all  faucets  or  other  contrivances  by  which  it 
might  be  obtained  for  drinking-water  by  careless  citizens. 
Such  a  supply,  for  fires  only,  has  been  introduced  at  Mil- 
waukee, Detroit,  Buffalo,  Boston,  and  Cleveland;  and  for 
manufacturing  purposes  at  New  London,  Conn.  Salt  water 
has  been  used  for  street-sprinkling  and  sewer-flushing  in  a 
number  of  English  cities,  where  it  is  said  to  prove  very  satis- 
factory; one  gallon  of  sea- water  laying  the  dust  as  effectively 
as  three  or  four  of  fresh.  New  York  City  has  discussed  the 
advisability  of  introducing  an  auxiliary  salt-water  fire  system 
for  the  business  section.     Tiie  chief  reason  for  introducmg  an 


370  WA  TER-SUPPL  V  ENGINEERING. 

auxiliary  fire  system  is  not,  however,  scarcity  of  supply,  but 
the  possibility  of  thus  obtaining  greater  pressure  and  rate  of 
discharge;  and  the  use  of  such  a  system  in  no  way  affects  the 
selection  of  a  source  of  supply  for  domestic  consumption. 

In  searching  for  a  watershed  to  supply  surface-water,  it  is 
desirable  to  find  one  from  which  the  water  can  be  led  by 
gravity,  and  this  will  generally  be  at  the  head-waters  of  a 
stream  passing  through  or  near  the  city,  or  of  one  of  its 
tributaries.  This  shed  should  be  comparatively  free  from 
occupants,  and  preferably  wooded  and  without  swamps.  The 
drainage  area  necessary  may  be  calculated  by  dividing  the 
maximum  annual  supply  desired  plus  evaporation  from  the 
reservoir  by  the  expected  yield  per  square  mile.  This  yield 
may  be  the  average  annual  yield,  but  not  unless  a  very  large 
storage-reservoir  is  provided.  It  would  be  better  to  use  the 
minimum  average  yield  of  three  or  four  years.  Great  care 
and  judgment  should  be  used  in  estimating  the  rate  of  yield, 
all  rainfall,  evaporation,  and  stream-flow  data  available  being 
used  as  outlined  in  Art.  31.  The  most  reliable  data  are  those 
obtained  by  careful  run-off  or  stream-flow  gaugings  on  water- 
sheds in  the  same  section  of  country  and  general  topographical 
location,  correcting  these  for  different  areas  of  water-surface 
if  necessary.  If  no  such  data  have  been  obtained,  use  may 
be  made  of  the  general  rainfall  and  run-off  records  for  that 
section  of  the  country,  as  given  in  Chapters  V  and  VI  or 
obtained  from  government  records.  The  less  reliable  and 
specific  the  data,  the  greater  the  amount  of  surplus  catchment 
area  which  should  be  provided  above  that  estimated. 

The  size  of  catchment  area  having  been  determined,  a 
point  should  be  looked  for  in  the  drainage  valley  which  offers 
a  favorable  location  for  a  dam  and  reservoir  and  above  which 
the  extent  of  drainage  area  is  at  least  that  found  necessary. 
This  point  should  also  be  at  such  elevation  above  the  city  or 
irrigation-fields  that  water  can  be  delivered  there  by  gravity 


DESIGNING.  371 

and  with  the  desired  pressure.  If  one  area  cannot  be  found 
sufficiently  large  to  furnish  the  entire  supply,  several  may  be 
used,  the  nearer  they  are  to  each  other  and  to  the  point  of 
utilization  the  better.  A  large  city  may  be  compelled  to  go 
a  long  distance  for  the  necessary  supply;  as  did  New  York 
City;  and  Liverpool,  whose  supply  is  impounded  68  miles 
distant.  Philadelphia,  also,  has  considered  the  advisability  of 
going  to  the  head -waters  of  the  Delaware  River  for  her 
supply. 

The  best  reservoir-location  is  one  at  which  the  desired 
quantity  can  be  stored  on  the  least  surface  area,  and  where 
the  shores  of  the  reservoir  will  be  fairly  steep;  also  where  the 
impounding-dam  may  be  short,  have  a  solid  foundation,  and 
be  constructed  largely  of  material  found  near  at  hand.  A 
bowl-shaped  basin  among  the  hills  or  mountains,  having  a 
narrow  gorge  for  its  outlet,  best  fulfils  these  conditions. 
Reservoirs  have  been  built  in  a  rolling  country,  however, 
where  the  length  of  the  dam  is  as  great  as  that  of  the  reser- 
voir, and  the  maximum  depth  but  a  few  feet;  but  such 
reservoirs  lose  much  of  their  stored  water  through  evaporation 
and  seepage,  and  are  liable  to  acquire  undesirable  qualities. 

The  geological  conditions  of  a  reservoir-site  should  be 
such  that  there  is  little  danger  of  leakage;  the  strata  being 
synclinal  rather  than  anticlinal,  and  containing  no  fissures  or 
open  faults. 

In  searching  for  a  ground-water  supply,  if  shallow  wells 
or  filter-galleries  are  proposed  no  data  concerning  the  flow  to 
be  expected  can  be  obtained  from  points  more  than  a  very 
few  miles  away;  except  as  these  have  thrown  light  on  the 
general  laws  of  ground-flow.  Test-wells  and  pumping  should 
form  the  chief  basis  of  estimating  the  flow.  In  this,  as  in 
tests  of  deep  wells,  pumping  should  be  continued  for  a  con- 
siderable time;  and  it  is  desirable  to  sink  another  observation- 
well  at  some  distance — say   1000  feet — away,   and  note  the 


372  iVA  TER-SUPPL  V  ENGINEERING. 

fluctuations  of  ground-water  level  in  it.  If  this  constantly 
falls  while  pumping  at  a  uniform  rate  is  continuing,  it  indi- 
cates that  not  only  is  all  of  the  regular  ground-flow  being 
pumped,  but  the  ground-storage  is  being  drawn  upon.  The 
water-surface  in  the  observation-well  may  be  lowered  during 
the  first  day  or  two  of  pumping,  even  if  this  be  less  than  the 
rate  of  ground-flow,  but  after  the  conditions  of  flow  to  the 
well  become  established  it  should  remain  stationary.  If  the 
pumping  could  be  continued  at  the  maximum  rate  which  it 
is  possible  to  maintain  without  drawing  upon  the  storage, 
this  would  equal  the  ground-flow  at  that  time.  But  it  must 
be  remembered  that  shallow  wells  are  much  more  affected  by 
droughts  than  are  deep  ones. 

Of  deep  wells  also  the  only  sure  knowledge  can  be 
obtained  by  actual  test;  but  if  there  are  others  in  the  vicinity, 
much  may  be  judged  from  their  performance.  If  these  tap 
water-bearing  sandstones  or  other  rock  strata,  the  prob- 
abilities are  that  wells  of  similar  capacity  and  characteristics 
may  be  driven  to  the  same  rock  over  a  considerable  section 
of  country;  as  in  the  case  of  the  Dakota,  St.  Paul,  and  other 
sandstones  in  the  North-central  States.  If  the  wells  are  in 
glacial  deposits,  the  extent  of  the  strata  which  they  tap  is  very 
uncertain  and  can  be  known  only  by  actual  investigation. 

If  the  amount  of  water  desired  is  small,  the  possibility  of 
obtaining  it  from  springs  should  not  be  overlooked,  and  suit- 
able ones  should  be  searched  for.  On  the  other  hand,  the 
limit  of  area  to  be  investigated  for  supplies  is  generally 
limited  by  the  small  amount  of  money  available  for  construct- 
ing conduits  in  a  small  plant. 

It  will  generally  be  desirable  to  make  comparative  esti- 
mates of  the  cost  of  using  each  of  the  available  sources; 
never  forgetting  that  quality  should  outweigh  any  financial 
considerations  where  the  water  is  for  domestic  use. 


designing.  373 

Art.  89.     The  General  Design. 

The  location  of  the  source  of  supply  will  generally  deter- 
mine whether  the  system  will  be  a  gravity  or  a  pumping  one; 
and  the  two  may  be  combined,  either  when  there  are  two 
sources  of  supply,  or  when  the  territory  to  be  supplied  is  at 
different  elevations.  In  the  latter  case  there  will  generally 
be  a  high-service  distributing-reservoir  into  which  the  water 
is  pumped;  in  the  former  the  pumping  and  gravity  supplies 
may  be  distributed  by  practically  two  separate  systems,  or, 
as  is  more  often  the  case,  pumping  is  resorted  to  to  supple- 
ment the  gravity  supply  when  this  becomes  deficient.  If  the 
storage-reservoir  is  at  a  great  distance  from  or  elevation  above 
the  city,  a  smaller  distributing-reservoir  is  desirable.  The 
top  of  a  hill  or  ridge  immediately  above  the  city  and  150  to 
300  feet  higher  forms  the  best  location  for  such  a  reservoir; 
or  a  flat  slope  on  a  side  hill  may  be  used.  If  such  a  location 
is  not  obtainable  and  the  storage-reservoir  is  more  than  300 
to  350  feet  higher  than  the  city,  in  which  case  a  distributing- 
reservoir  is  desirable  to  prevent  a  pressure  head  dangerous  to 
ordinary  plumbing,  this  may  sometimes  be  located  lower 
down  the  valley  of  the  impounded  stream  and  formed  by  a 
small  dam  across  this  valley,  the  old  stream-bed  serving  as  a 
conduit  to  connect  the  two  reservoirs.  But  if  the  watershed 
above  the  distributing-reservoir  is  liable  to  pollute  the  supply, 
the  distributing-reservoir  should  be  placed  out  of  the  channel 
of  flow. 

If  pumping  is  employed,  a  reservoir  or  standpipe  is 
extremely  desirable,  and  should  be  omitted  only  when  it  is 
impossible  to  obtain  the  money  to  pay  for  it;  and  even 
then  its  future  construction  should  be  provided  for,  and 
carried  out  as  soon  as  possible.  Whether  reservoir  or  stand- 
pipe  is  provided  will  generally  depend  upon  the  local  topog- 
raphy.     A  reservoir  is  to   be  preferred  if  a  hill  sufficiently 


374  WATER-SUPPLY  ENGINEERING. 

high  for  one  is  near  the  city;  but  if  there  is  no  such  hill,  a 
standpipe  will  be  necessary  to  give  the  desired  elevation  and 
head  of  water.  A  standpipe  may  be  placed  anywhere  in  a 
city,  as  it  occupies  but  little  ground  space,  and  is  more 
efficient  the  nearer  it  is  to  the  centre  of  the  district  most 
urgently  requiring  fire-protection — generally  the  business  or 
manufacturing  district. 

The  elevation  of  the  reservoir  or  standpipe  will  determine 
the  volume  and  range  of  fire-streams  in  the  city,  since  the 
pressure  at  the  nozzle,  plus  the  friction  loss  in  the  hose  and 
pipes  between  this  and  the  reservoir  or  standpipe,  must 
equal  the  difference  in  level  between  the  nozzle  and  the  sur- 
face of  the  stored  water.  (The  velocity-head  will  be  so  small 
as  to  be  negligible.)  Knowing  the  volume  and  range  of  fire- 
streams  and  the  number  of  simultaneous  streams  desired,  and 
the  size  and  length  of  pipes  between  the  nozzle  and  supply, 
the  velocity  in  these  last  can  be  calculated  and  from  this  the 
friction-head ;  and  friction-head  plus  nozzle  pressure-head 
pJus  elevation  of  the  principal  fire  district  will  give  the  desired 
elevation  of  the  water  in  reservoir  or  standpipe.  A  stand- 
pipe  should  be  carried  at  least  15  to  20  feet  above  this  eleva- 
tion, since  the  water-level  falls  rapidly  during  fires. 

In  the  case  of  a  large  city  in  a  level  country  such  a 
condition  is  practically  impossible  unless  a  number  of  stand- 
pipes  be  scattered  throughout  the  city.  (In  such  a  location 
the  supply  will  in  every  case,  probably,  be  by  pumping.)  It 
then  becomes  necessary  to  obtain  additional  head  by  pumping 
during  fires.  This  may  be  effected  either  by  the  use  of 
steam  fire-engines,  in  which  case  the  head  in  the  water-mains 
must  be  sufficient  to  supply  water  to  the  fire-hydrant  at  the 
maximum  rate  at  which  the  fire-engines  can  use  it;  or  the 
pressure  and  volume  given  by  the  water-works  engines  may 
be  increased  when  a  fire  breaks  out,  the  reservoir  or  stand- 
pipe  being  at  the  same  time  shut  off  from  the  system.     The 


DESIGNING.  375 

objections  to  the  latter  plan  are,  that  a  longer  time  is 
generally  consumed  in  raising  the  pressure  at  the  pumping- 
station  than  in  starting  a  fire-engine;  and  pipes  and  fixtures 
which  showed  no  sign  of  weakness  during  ordinary  service- 
pressure  are  apt  to  be  broken  by  the  excessive  fire-pressure. 
Both  these  objections  are  found  to  be  most  seriously  applica- 
ble to  four  out  of  five  of  the  smaller  cities  and  towns. 

If  the  supply  for  a  pumping  system  be  from  ground-water 
or  other  source  not  subject  to  occasional  pollution  with  con- 
siderable suspended  matter,  or  if  it  be  filtered,  an  excellent 
arrangement  is  to  place  the  pump  and  the  reservoir  or  stand- 
pipe  on  opposite  sides  of  the  city,  and  use  the  direct-indirect 
system.  If  the  main  break  near  either  pump  or  reservoir,  the 
other  of  the  two  can  then  supply  the  entire  city;  and  with  a 
proper  arrangement  of  piping  it  will  be  impossible  for  any 
one  break  to  deprive  more  than  one  city  block  of  its  supply. 
Also  a  more  generally  uniform  fire-pressure  can  be  obtained 
thus  than  if  pump  and  reservoir  were  on  the  same  side  of  the 
distribution  system. 

If  the  supply  is  from  a  river,  however,  and  is  not  filtered, 
the  pumps  should  preferably  discharge  directly  into  reser- 
voirs, that  the  water  may  have  some  opportunity  for  clarifica- 
tion when  muddy  before  being  delivered  for  consumption. 
At  least  two  reservoirs,  or  one  double  reservoir,  should  be 
provided,  and  these  should  always  be  kept  full  while  the 
river- water  is  clear,  to  furnish  the  supply  while  it  is  muddiest; 
being  if  possible  of  such  size  as  to  furnish  the  supply  until 
the  river-water  again  becomes  clear.  The  further  a  river- 
valley  extends  above  the  intake  the  longer  will  this  period  of 
turbidity  continue.  The  period  will  vary  widely  with  the 
character  of  soil  and  slope  of  the  watershed,  but  for  average 
conditions  the  turbidity  will  probably  continue,  after  a  heavy 
rain  ceases,  one  day  for  each  30  to  50  miles  of  river  above. 

Where  there  is  no  location  for  distribution-reservoirs  in  a 


37^  WATER-SUPPLY  ENGINEERING, 

river  pumping-system,  it  is  advisable  to  place  settling-reser- 
voirs near  the  river  at  the  pumping-station,  and  pump  into 
these,  and  from  them  to  a  standpipe  by  the  direct-indirect 
system.  The  same  pumps  could  be  used  alternately  for 
pumping  from  river  to  reservoir  and  from  reservoir  to  stand- 
pipe;  but  greater  economy  could  generally  be  obtained  by 
using  for  the  former  centrifugal  pumps  of  high  efificiency,  and 
reciprocating  pumps  for  the  service-pumping,  both  being  run 
by  the  same  steam-plant. 

A  by-pass  should  be  provided  around  the  distributing- 
and  settling-reservoirs  from  the  pumping  to  the  distribution 
main,  to  be  used  for  direct  pumping  if  it  is  desired  to  clear  or 
repair  the  reservoirs,  or  to  increase  the  pressure  during  fires. 

An  uncontaminated  supply  is  more  satisfactory  and  reli- 
able than  a  purified  one,  but  the  latter  is  infinitely  preferable 
to  a  contaminated  one  unpurified.  If  purification  is  neces- 
sary, the  works  may  be  immediately  below  a  storage- 
reservoir,  but  would  generally  be  more  accessible  just  above 
a  distributing  one.  In  the  case  of  a  pumping  supply,  an 
excellent  location  for  a  gravity  purification-plant  is  between 
the  sedimentation-basin  and  the  main  pumps;  or,  if  there  be 
no  sedimentation-basins,  the  purification-plant  should  be 
between  the  river  and  the  pumps,  secondary  pumps  raising 
the  water  to  it  from  the  river  if  necessary.  If  pressure 
mechanical  filters  be  used,  these  may  be  placed  near  the 
pumps  on  the  pumping-main,  water  being  pumped  through 
them  directly  from  the  river.  But  the  life  and  efficiency  of 
both  pumps  and  filters  will  generally  be  increased  by  first 
clarifying  the  water  in  a  sedimentation-basin. 

Art.  90.     Details  of  Gravity  Head-works. 

The  investigation  of  a  watershed  calls  for  accurate  data 
concerning    its    area  and   form.      These   may  sometimes  be 


DESIGNIXG.  Z77 

obtained  from  State  or  government  works;  but  in  most  cases 
it  is  necessary  to  make  the  required  surveys.  The  most 
important  of  these  is  a  careful  running  of  a  transit-line  around 
the  boundary  of  the  catchment  area,  and  a  line  of  levels 
(referred  to  the  city  elevation)  and  transit-line  up  the  bottom 
of  the  drainage  valley.  From  a  map  prepared  from  these 
data  the  catchment  area  above  any  proposed  dam-site  can  be 
scaled  off,  and  its  total  yield  estimated;  and  the  head  available 
at  the  city  or  irri^  ition-fields  due  to  the  elevation  of  the  dam 
may  be  learned. 

At  the  dam-site  selected,  borings  or  test-pits  should  be 
made  to  determine  the  character  of  the  underlying  strata. 
These  should  be  located  at  several  points  over  the  site  to  be 
covered  by  the  dam,  and  also  over  the  reservoir  area.  An 
impervious  stratum  should  not  be  pierced  by  the  test-holes; 
but  if  found  to  exist  under  the  dam-  and  reservoir-site,  other 
test-holes  a  short  distance  below  the  dam-site  should  be 
carried  through  or  several  feet  into  the  impervious  stratum  to 
learn  if  its  thickness  be  sufficient.  If  this  be  more  than  one 
third  the  height  of  the  dam  and  the  material  be  solid,  it  can 
probably  be  relied  upon  as  a  foundation.  If  less  than  this 
be  found,  with  a  soft  or  porous  material  underlying  it,  further 
investigation  should  be  made  before  finally  selecting  the  site; 
although  an  earth  dam  would  probably  be  safe  upon  a  con- 
siderably thinner  rock-foundation  if  free  from  seams  or  cracks. 
The  danger  from  a  thin  impervious  stratum  is  twofold:  its 
strength  may  not  be  sufficient  to  support  the  dam,  or  the 
head  of  water  created  may  cause  a  leakage  through  it. 

A  thorough  investigation  should  be  made,  if  necessary, 
to  render  certain  and  exact  the  information  concerning  the 
geological  formation  at  the  dam-site.  Such  conditions  as  are 
shown  in  Fig.  56  are  inadmissible.  In  a  leakage  would  almost 
surely  occur  under  the  dam.  In  b  it  would  penetrate  the  rock 
and  the  under-stratum  in  consequence  of  the  head  created 


378 


PFA  TER-SUPPL  Y   ENGINEERING. 


behind  the  dam,  and  either  a  leak  result  or  the  under-stratum 
become  saturated  and  soft;  in  either  of  which  cases  the  rock 
would  be  likely  to  yield  under  the  weight  of  the  dam.  In  b 
the  dam  should  be  carried  down  to  a  thick  stratum  of 
unseamed  rock  or  moved  to  another  location,  as  below  the 
point  c.  In  a  the  core-wall  may  be  carried  to  the  lower 
rock-stratum,  unless  this  also  is  underlaid  by  a  porous  stratum 
which  outcrops  within  the  reservoir  area. 

Not  only  the  bottom,  but  the  sides  also  of  the  valley 
should  be  carefully  examined   for   seams,    porous   strata,   or 


Fig.  56. — Unsuitable  Dam-sites. 

other  conditions  which  would  cause  leakage  under  or  around 
the  dam. 

From  the  size  of  the  catchment  area  and  the  estimated 
yield,  the  amount  of  storage  required  can  be  estimated  (see 
Art.  33).  This  capacity  is  then  used  to  learn  the  height  of 
dam  necessary.  A  carefully  prepared  contour-map  of  the 
reservoir-site  is  made,  the  contour  interval  being  from  i  to  5 
feet,  depending  upon  the  steepness  of  the  ground-slope. 
The  dam  is  approximately  located  on  this.  Beginning  at  the 
lowest  contour,  the  area  included  by  this  above  the  dam  is 
measured  by  a  planimeter  or  otherwise;  and  the  sam.e  is 
done  with  each  successive  contour;  the  volumes  embraced 
between  successive  contour-planes  is  calculated,  and  when  the 
sum  of  all  these  volumes  below  a  certain  plane  equals  the 
amount  of  storage  desired,  this  contour-plane  will  be  the 
elevation  of  the  reservoir  spillway.     The  water  will  rise  such 


DESIGNING.  379 

a  distance  higher  than  this  as  is  necessary  to  discharge  the 
maximum  floods  over  the  spillway. 

If  a  storage-reservoir  of  the  desired  capacity  would  require 
a  very  high  dam,  it  may  in  some  cases  be  cheaper  to  construct 
two  reservoirs,  either  one  below  the  other  in  the  same  valley, 
or  in  different  valleys. 

If  the  back-water  from  the  reservoir  will  cause  shallow 
ponding  of  water  along  the  banks  of  the  tributary  stream, 
the  channel  of  this  should  be  walled  in  and  the  banks  raised 
above  the  water-level  of  the  reservoir;  and  the  same  treat- 
ment, or  excavation  and  paving,  or  more  often  both  combined 
as  at  b.  Fig.  57,  should  be  applied  to  all  shallow  water  within 


Fig.  57. — Reservoir  Cross-section. 
the  limits  of  the  reservoir.  If  a  shallow  pond  is  formed,  as 
at  a,  it  will  generally  be  better  to  fill  this  entirely,  as  shown 
by  the  dotted  lines.  Sufficient  material  for  this  will  in  most 
cases  be  obtained  in  clearing  off  the  reservoir-site  and  grading 
the  banks.  The  last  few  feet  nearest  the  slope  of  this  fill, 
however,  should  be  of  gravel  or  earth  free  from  organic 
matter.  Embankment-slopes  should  be  paved  with  dry  slope- 
wall;  and  it  is  desirable  to  treat  the  entire  shore  of  the 
reservoir  in  this  manner. 

The  decision  as  to  the  material  of  which  a  dam  should  be 
constructed  will,  to  a  large  extent,  depend  upon  the  size  of 
the  dam,  character  of  the  foundation,  the  material  at  hand, 
the  accessibility,  and  the  money  available.  If  bed-rock  is 
near  the  surface  and  can  be  quarried  for  construction  near 
by,  a  masonry  or  rock-fill  dam  is  easily  possible.  If  hardpan 
or  clay  is  near  the  surface  and  good  embankment  materials 


380  WATER-SUPPLY  ENGINEERING. 

near  at  hand,  an  eaith  dam  is  practicable.  If  rock  exists  for 
a  foundation  and  for  masonry,  and  also  soil  adapted  to 
embankments,  either  construction  is  possible.  Where  labor, 
cement,  and  sand  are  reasonably  cheap  an  earthen  embank- 
ment more  than  70  or  80  feet  high  will  probably  cost  more 
than  a  masonry  dam,  owing  to  the  great  width  of  the  base 
and  volume  of  material  in  the  former.  If  the  dam  is  short 
and  the  spillway  must  be  placed  in  it,  this,  which  must 
generally  be  of  masonry,  may  form  so  large  a  proportion  of 
the  dam  that  constructing  the  whole  of  masonry  as  a  weir- 
dam  would  cost  but  little  more,  and  would  be  much  safer. 

If  no  rock,  hardpan,  or  clay  exist  within  40  or  50  feet  of 
the  surface  to  form  a  foundation  and  impervious  bottom  for 
the  reservoir,  it  will  probably  be  well  to  endeavor  to  find 
another  site.  If  the  site  selected  be  not  underlaid  with  such 
a  stratum  of  considerable  thickness  it  would  be  useless  to 
place  there  a  tight  masonry  or  earth  dam  of  considerable 
height;  but  one  10  or  15  feet  high  may  be  constructed  on  a 
timber  foundation  protected  by  sheet-piling  (see  Fig.  25, 
page  244),  although  this  construction  is  to  be  avoided  if 
possible.  In  such  a  location  a  rock-fill  or  timber  dam  may 
be  used  to  divert  the  water  if  no  storage  be  required. 

The  general  form  and  cross-section  of  dams  has  been 
already  considered  in  Chapter  XII.  The  cubic  contents  of  a 
given  dam  can  be  most  readily  ascertained  by  the  use  of  a 
contour-map  of  the  site,  to  a  large  scale.  The  method  is 
illustrated  in  Fig.  58.  On  the  prolonged  axis,  AB,  of  the 
dam  a  cross-section  of  the  same,  CDEF,  is  drawn  to  the  same 
scale  as  the  contour-map  and  with  AB  as  its  vertical  axis. 
If  the  crest  of  the  dam  is  to  be  at  an  elevation,  say,  of  125 
feet  above  datum,  horizontal  lines  are  drawn  at  intervals  of 
5  feet  (if  this  be  the  contour-interval)  beneath  this  and 
numbered  with  their  proper  elevations.  The  points  of  inter- 
section of  the   120  line  are  projected  down   to  the  map,  and 


DESIGNING. 


381 


where  the  projection  lines  cut  the  120-foot  contours,  as  at 
^>  /,  g,  and  h  are  points  in  the  junction  of  the  dam  and  the 
earth  surface,  ef  and  gh  are  connected ;  a,  b,  d,  and  r,  are 
found  and  connected  in  the  same  way,  and  a  is  connected 
with  r,  b  with  /,  etc.,  the  outline  aekfbdglhc,  being  thus 
formed.  The  areas  acdb,  ehgf,  etc.,  are  now  measured  and 
treated  as  parallel  section  of  a  prismoid  in  calculating  the 
cubic  contents  of  the  dam.     The  contours  ac,  bd,  fg,  and  eh 

126 


Fig.  58. — Estimating  Contents  of  Earth  Dam. 
are  taken  as  the  ends  of  the  horizontal  sections.  Instead  of 
using  surface-contours,  those  of  the  ground  as  cleared  or 
excavated,  or  of  the  rock,  if  it  be  a  masonry  dam,  should  be 
used;  or  the  surface-contours  may  be  used,  and  to  the  result- 
ing calculation  may  be  added  the  amount  to  be  excavated 
and  then  refilled  as  embankment  or  masonry. 


382  WATER-SUPPLY  ENGINEERING. 

The  upper  face  of  earth  dams  should  be  protected  from 
wash,  weeds,  and  ice  by  paving.  This  is  generally  in  the 
form  of  a  dry  wall  12  to  24  inches  thick,  composed  of  a 
single  layer  of  flat  stone,  carefully  laid  by  hand  on  a  bed  of 
coarse  gravel  or  broken  stone  6  to  20  inches  thick.  A  bed 
of  concrete  4  to  12  inches  is  better  than  the  broken  stone; 
and  when  this  is  used  brick  is  in  many  cases  substituted  for 
the  dry  stone  wall. 

The  concrete  may  be  made  practically  impervious  if  this 
is  desirable;  or  asphalt  may  be  used  to  obtain  a  tight  lining 
in  one  of  the  ways  described  in  Art.  73.  The  outer  slope  of 
a  dam  is  generally  sodded  to  prevent  wash  by  rains;  although 
in  some  cases  this  also  has  been  paved.  If  there  is  a  berme, 
a  paved  gutter  should  be  placed  along  the  inner  edge  of  this, 
leading  to  a  drain  which  discharges  upon  the  natural  surface 
below  the  dam. 

The  face  of  a  masonry  dam  may  be  vertical,  sloping, 
curved,  or  stepped.  The  first  is  applicable  to  very  low  dams 
only,  the  second  to  dams  up  to  20  to  30  feet  in  height  if 
never  overflowed,  but  only  10  or  15  feet  if  ever  acting  as 
weirs.  Weir-dams  from  10  or  15  to  20  or  30  feet  high 
should  be  stepped  in  front.  Dams  more  than  30  or  40  feet 
high  should  be  given  forms  calculated  for  greatest  economy; 
as  the  "  economical  "  or  the  new  Croton  profile  in  Plate  XV, 
page  258;  and  if  to  act  as  weir-dams  should  have  an  ogee  or 
other  curved  face,  similar  to  the  Austin  or  Holyoke  dam 
(Plates  XIV  and  XV,  pages  256  and  258).  The  face-stones 
may  all  rest  on  horizontal  beds,  but  in  weir-dams,  at  least,  it 
is  better  to  make  the  joints  radial,  as  in  Plate  XIV. 

The  crest-  or  cap-stones  should  be  heavy  and  substantial, 
and  where  there  is  great  danger  from  heavy  logs  and  ice  they 
may  be  bound  together  as  in  the  Holyoke  dam.  For  spill- 
ways in  storage-reservoirs,  however,  the  construction  shown 
in  Fig.  59  will  generally  be  suflficient,  the  steps  being  some- 


DESIGNING. 


383 


times  replaced  by  an  ogee  face  for  high  spillways.  If  the 
main  dam  be  of  earth  and  a  masonry  core-wall  be  used,  it 
should  be  joined  to  the  masonry  of  the  spillway;  or  if  there 
be  no  core-wall,  a  spur-wall  should   be  carried  for  some  dis- 


VERTICAL 
SECTION 


Fig.  59. — Spillway  in  Earth  Embankment. 

tance  into  the  centre  of  the  embankment  from  each  end  of 
the  spillway.  A  spillway  over  natural  bed-rock  at  the  head 
of  the  dam  is  generally  preferable  to  a  weir. 

The  cut-off  flanges  for  pipe  passing  through  an  embank- 
ment or  dam  may  be  made  as  shown  in 
Fig.  60.  A  thin  sheet  of  lead  or  other  yield- 
ing and  durable  material  should  be  placed 
between  the  casting  and  the  pipe,  and  between 
the  flanges  of  the  casting,  so  that  no  water 
may  work  its  way  between  the  pipe  and  cut-off  pj^,  ^q  _flan 
flange. 

But  one  pipe,  an  outlet-main,  may  be  used 
in  small  reservoirs,  a  blow-off   branch    being  placed  on   this 


GE 

FOR  PiTE  IN  Em- 
bankment. 


384 


WATER-SUPPLY  ENGINEERING. 


just  outside  the  reservoir  and  controlled  by  proper  valves. 
The  inner  end  of  such  pipe  must  be  at  the  lowest  point  in 
the  reservoir  and  flush  with  the  bottom,  in  order  that  the 
water  may  all  be  drawn  off.  It  should,  however,  be  supplied 
with  a  removable  extension  rising  at  least  a  foot  or  two  above 
the  bottom,  to  exclude  mud  and  other  deposits  from  the 
outlet-main  during  service.      This  riser  should  terminate  in  a 


Fig.  6i. — Outlet-pipe  for  Small  Reservoirs. 

screen  to  keep  out  fish  and  other  large  matters.  The  gates 
controlling  the  flow  from  the  reservoir  can  be  placed  outside 
the  embankment  in  a  manhole  or  gate-house.  This  is  the 
simplest  arrangement  practicable,  and  is  applicable  to  the 
smallest  reservoirs  only;  and  even  in  these  a  separate 
**  mud-"  or  '*  waste-"  pipe  is  preferable. 

Such  a  screen  as  is  here  referred  to  cannot  well  be  cleaned 
without  removing  it  entirely.  Also  if  any  break  or  leak 
occur  in  the  outlet-pipe  above  the  gate,  the  flow  through  it 
cannot  be  stopped  except  by  emptying  the  reservoir,  before 
which  the  bank  would  probably  be  destroyed.  It  is  hence 
better  to  provide  gates  on  the  outlet-pipe  inside  the  reser- 
voir; and  duplicate  screens  which  can  be  removed  for  cleaning 
and  replaced  without  leaving  the  outlet  unprotected;  and 
this  is  always  done  in  large  reservoirs.  A  vertical  flat  screen 
does  not  become  obstructed  so  quickly  as  a  horizontal  one 
and  is  more  easily  removed  and  cleaned,  and  is  consequently 


DESIGNING. 


385 


preferable.  Such  a  screen  may  be  made  of,  say,  No.  10 
"opper  wire,  ^-inch  mesh,  in  a  steel  frame;  but  a  copper 
plate,  punched  to  form  a  screen,  cleans  more  easily.  Wire 
screens  in  frames  of  almost  any  size  are  carried  in  stock  by 
companies  dealing  in  valves  and  other  water-works  supplies. 

The    form   of   gate-house  employed    is  ordinarily   on    the 
general  plan  of  that  shown  in  Fig.  62.     Any  one  screen  can 


PLAN 
Ofh  SLUICE  GATES,  hi,,  SCREENS.  r,f,<-,<-,  FLAS>J*B0ARD8 

Fig.  62. — Gate  house. 
(East  Branch  Reservoir,  New  York.) 


here  be  removed,  a  duplicate  one  meantime  being  in  service. 
The  discharge  from  the  reservoir  can  be  passed  through  any 
or  all  outlet-pipes,  each  of  which  is  controlled  by  a  gate 
worked  from  above  by  a  stem  and  wheel.      Water  enters  the 


386 


WA  TER-SUPPL  y  ENGINEERING. 


gate-house  from  the  reservoir  through  several  openings  in  the 
wall  AB,  which  are  placed  at  different  elevations  and  con- 
trolled by  sluice-gates  (Fig,  63)  to  permit   of  drawing  water 


Fig.  63. — Reservoir  Sluice-gate. 

from  any  depth,  and  thus  securing  the  purest  and  coolest. 
The  lowest  one  should  be  a  little  lower  than  any  part  of  the 
reservoir  bottom,  and  is  used  for  emptying  the  reservoir,  or 
drawing  off  the  foulest  water  before  the  "  turn-over,"  through 
a  mud-  or  waste-pipe,  which  discharges  below  the  dam, 
generally  in  the  old  creek-bed.  The  outlet-pipes  and  gate- 
house demand  the  most  careful  attention,  the  firmest  founda- 
tion, and  the  most  substantial  construction.  The  foundation 
of  the  gate-house  should  rest  on  the  same  material  as  does 


DESIGXIXG.  387 

the  dam  or  core-wall.  The  bottom  should  be  absolutely 
water-tight;  if  not  on  rock,  a  broad  thick  bed  of  concrete 
forms  probably  the  most  desirable  foundation.  The  wall  of 
the  gate-house  should  be  of  small  uncourscd  ashlar,  in  the 
best  of  Portland  cement-mortar,  with  walls  of  such  thickness 
that  no  stone  reaches  entirely  through  them,  the  idea  being 
to  make  them  water-tight  and  sufificiently  strong  to  support 
the  outside  water-pressure  when  the  gate-house  is  empty,  or 
the  pressure  of  ice.  The  construction  of  the  gate-house 
should  be  such  as  to  prevent  its  injury  by  ice  if  the  water  in 
the  reservoir  rises  or  falls  while  frozen  over,  or  by  the  expan- 
sion of  ice  between  it  and  the  dam.  To  insure  this  it  is 
generally  better,  if  the  dam  be  of  masonry,  to  have  the  gate- 
house built  against  or  as  a  part  of  it.  In  the  case  of  earth 
dams,  the  gate-house  is  generally  at  the  inside  foot  of  the 
embankment,  and  communication  with  it  is  afforded  by 
means  of  a  foot-bridge  from,  and  on  a  level  with  the  top  of, 
the  embankment.  In  a  few  cases  the  gate-house  has  been 
formed  by  sinking  a  well  in  the  rock  at  one  end  of  the  dam, 
and  filling  it  through  a  tunnel  or  open  cut  carried  from  it  into 
the  reservoir;  this  plan  avoiding  the  weakening  of  the  dam 
by  the  outlet-pipes.  In  the  Oak  Ridge  (East  Jersey  Water 
Company)  Reservoir  this  plan  was  adopted,  the  gate-house 
and  inlet-  and  discharge-channels  being  more  than  40  feet 
deep  in  solid  bed-rock.  The  gate-house  is  floored  over, 
generally  on  a  level  with  the  top  of  the  dam ;  and  is  covered 
with  a  small  building  to  protect  the  gates  and  exclude  med- 
dlesome intruders.  This  building  is  frequently  given  an 
attractive  appearance. 

The  outlet-pipes  should  make  a  water-tight  connection 
with  the  gate-house,  and  be  placed  on  a  perfectly  firm  foun- 
dation, that  they  may  not  be  broken  by  settlement.  The 
bottom  of  the  reservoir,  for  several  feet  in  front  of  the  gate- 
house inlet-opening,  should  be  paved  to  prevent  washing. 


388 


WATER-SUPPLY  ENGINEERING. 


Where  a  storage-reservoir  is  not  necessary  and  a  diverting- 
dam  only  is  provided,  the  water 
is  generally  drawn  off  from  at  or 
near  the  surface  of  the  stream. 
For  this  purpose,  instead  of  a 
gate-house  and  pipes,  an  opening 
is  ordinarily  made  in  one  end  of 
the  dam,  leading  to  an  open  con- 
duit ;  this  opening  being  controlled 
by  sluice-gates.  In  addition  to 
the  gates  it  is  generally  desirable 
to  place  in  front  of  them  an 
upright  grooved  frame  with  flash- 
boards  sliding  in  the  same,  and  a  contrivance  by  which  an 
opening  can  be  left  between  flash-boards  at  any  elevation  at 
which  it  is  desired  to  draw  off  the  water.  This  opening 
should  generally  be  kept  a  foot  or  two  below  the  water-surface, 
that  both  floating  brush,  leaves,  etc.,  and  the  heavier  matter 
carried  in  suspension  may  be  excluded  from  the  conduit.  As 
sand  and  gravel  will  probably  collect  in  front  of  the  flash- 
board  weir,  another  opening  is  generally  provided  in  the 
bottom  of  the  dam  near  this  weir  for  flushing  out  the  deposit 
at  intervals. 


Fig.  64. — Head-gates  and 
Flushing-out  Sluices. 


Art.  91.     Pumping-station  and  Inlet  Details. 


A  pumping-station  should  generally  be  located  as  near  as 
possible  to  the  body  of  water  from  which  it  draws,  to  reduce 
both  friction  in  the  suction-pipe  and  the  possibility  of  its 
leaking  air  and  reducing  the  vacuum.  The  boilers  should 
be  above  the  reach  of  floods;  and  their  foundation  should  be 
extremely  firm,  on  account  of  the  great  weight  to  be  sup- 
ported, which  may  amount  to  250,000  lbs.  or  more  for  each 
boiler.      The  pumps  must  also  be  protected  from  water,  but 


DESIGNING.  389 

it  may  be  necessary  for  them  to  be  below  high  water  (see 
Art.  84),  in  which  case  they  are  generally  placed  in  a  water- 
tight pump-pit,  as  in  Fig.  52,  page  348.  The  walls  of  this 
may  be  of  thick  brick,  concrete,  or  stone  masonry,  or  of 
sheet  iron  or  steel;  or  of  iron  and  masonry,  as  in  the  illustra- 
tion; and  the  well  is  usually  circular  in  plan,  this  giving  the 
greatest  strength.  To  reduce  the  size  and  cost  of  the  well 
the  pumping-engines  only  are  placed  in  it,  and  these  are 
generally  vertical  engines.  The  stairway  to  the  bottom  of 
the  well  can  be  made  to  follow  the  wall  in  a  large  spiral. 
A  water-tight  joint  must  of  course  be  made  where  the  suc- 
tion-pipe pierces  the  wall  of  this  well. 

If  the  pump  is  on  the  surface,  the  suction-pipe  should  be 
carried  several  feet  beneath  the  ground-level  before  leaving 
the  building,  and  be  kept  at  this  depth  until  reaching  the 
water,  to  prevent  its  freezing  in  winter.  The  suction-pipe 
should  be  larger  than  the  discharge;  and  if  of  considerable 
length  should  be  of  such  size  that,  when  all  the  pumps  are  in 
service,  the  velocity  of  flow  through  it  will  not  exceed  2  to  4 
feet  per  second  for  12-  to  36-inch  suctions  respectively. 
It  should  be  laid  with  unusual  care  to  obtain  tight  joints. 
It  should  not  terminate  in  a  river  or  lake  wall  nor  near 
the  bank  or  shore,  as  the  water  here  is  more  liable  to 
contain  fresh  sewage  and  floating  matter  than  in  mid-stream. 
The  best  location  and  design  of  the  inlet  will  vary  with  the 
circumstances.  It  should  be  placed  where  the  water  is  purest; 
in  a  lake  especially  this  will  generally  be  the  furthest  possible 
from  the  shore.  It  should  be  in  deep  water,  as  this  is 
ordinarily  cooler;  but  should  not  be  near  the  bottom,  as  the 
most  sediment  is  carried  there.  An  excellent  plan  is  that  of 
terminating  the  inlet  in  a  tower  somewhat  similar  to  a  reser- 
voir gate-house,  there  being  several  openings  at  different 
levels  through  which  the  water  can  be  taken  as  desired.  In 
the  Nashville,  Tenn.,  water-works  this  tower  is  hexagonal  in 


390  WATER-SUPPLY  ENGINEERING. 

plan,  lO  feet  interior  diameter  and  85  feet  high,  of  stone 
masonry  on  solid  rock.  At  Cincinnati  is  a  masonry  intake 
about  140  feet  high,  the  range  of  river  height  being  over  70 
feet.  The  intake  for  the  Chicago  water-works  is  four  miles 
from  shore,  formed  of  a  circular  double  steel  shell  70  feet 
inside  diameter,  the  space  between  the  shells  being  filled  with 
concrete  so  as  to  form  a  wall  24  feet  thick;  the  whole  resting 
in  40  feet  of  water,  and  being  50  feet  high  to  the  bottom  of 
a  masonry  superstructure.  The  St.  Louis  masonry  inlet- 
tower  is  about  50  feet  high,  and  is  oval  in  plan,  with  an  ice- 
breaker pointing  up-stream.  The  Cleveland  intake  is  of  steel, 
somewhat  similar  to  the  Chicago  one,  100  feet  outside  and 
50  feet  inside  diameter;  located  in  49  feet  of  water,  and  con- 
nected with  the  shore  by  26,000  feet  of  9-foot  tunnel  lined 
with  12  inches  of  brickwork — the  longest  intake-tunnel  in  the 
world. 

Such  inlet-towers  must  be  substantial  and  massive  enough 
to  resist  water-currents,  ice,  or  floating  logs,  and  are  conse- 
quently expensive.  They  are  also  an  obstruction  to  the 
current  in  a  river,  and  to  shipping  in  a  navigable  water,  in 
which  situation  they  must  be  provided  with  a  light-house. 

Instead  of  a  tower,  a  submerged  crib  is  frequently  used, 
especially  in  smaller  plants.  This  should  be  placed  where 
there  is  least  danger  of  silting,  and  it  is  desirable  to  make  its 
height  about  one  third  the  depth  of  the  water,  with  limits  of 
3  to  15  feet.  This  structure  is  essentially  a  wooden  crib, 
weighted  with  stone  and  anchored  to  the  bottom  in  some 
way  to  prevent  movement  by  tides  or  currents,  this  being 
effected  by  surrounding  it  with  coarse  rip-rap,  or  piles,  or 
bolting  it  to  bed-rock.  It  may  have  openings  on  the  sides; 
but  it  is  in  most  cases  preferable  to  make  these  tight  and 
take  water  through  the  top  only,  which  is  provided  with  a 
coarse  grating.      The  suction-   or  intake-pipe  rises  into  the 


DESIGNING. 


391 


centre  of  this  crib.      Such   cribs  are  used  at  Duluth,  Minn., 
Erie,  Pa.,  and  many  other  places  (see  Fig.  65). 

The  total  area  of  the  inlet-openings  in  the  crib  should  be 
considerable  to  prevent  the  formation  of  a  vortex  in  the  water 


SECTION  ON  A-B"^ 


Fig.  65. — Erie,   Pa.,  Intake-crib. 

above,  which  will  cause  floating  matter  to  be  sucked  into  the 
main;  or  the  entrance  of  "  needle-"  or  "  anchor  "-ice,  which 
closes  the  openings  in  the  pier  or  crib,  or  in  the  intake-pipe, 
or  may  reach  and  stop  the  screens  or  even  the  pump.  A 
very  little  motion  will  serve  to  carry  the  ice-needles  down  and 
into  an  intake-crib,  and  several  cities  have  suffered  water- 
famines  for  hours  and  days  on  this  account. 

Intakes  for  small   plants  in  shallow  water  are  frequently 
not  provided  with  a  crib,  but  are  simply  an  upright  extension 


392  WATER-SUPPLY  ENGINEERING. 

of  the  suction-pipe,  brought  up  to  a  short  distance  below  the 
surface  and  surrounded  with  concrete  or  rip-rap,  and  in  some 
cases  with  piles  to  protect  it  from  boats  or  floating  logs.  A 
great  number  of  small  cities  use  such  intakes,  and  they  give 
fairly  good  service  in  many  cases.  In  fact,  if  the  water  is 
quite  shallow  the  use  of  a  crib  may  be  practically  impossible 
in  Northern  streams,  where  the  , going-out  of  the  ice  would 
carry  the  crib  with  it.  If  the  expense  is  not  prohibitive  it  is, 
in  such  a  case,  desirable  to  place  a  low  weir-dam  just  below 
the  intake,  to  raise  the  water-surface,  permit  the  use  of  a  crib, 
and  prevent  damage  to  the  intake  from  ice  and  floating 
timber. 

To  prevent  the  stoppage  of  an  intake-pipe  by  ice  several 
devices  have  been  used.  In  one,  compressed  air  is  carried  by 
a  small  pipe,  which  is  laid  in  or  fastened  to  the  outside  of  the 
intake-pipe,  and  delivered  under  the  horizontal  screen  which 
covers  the  intake-opening,  the  rising  bubbles  preventing  the 
ice  from  collecting.  In  another,  steam  from  the  engine-room 
is  applied  in  the  same  way.  A  "  rotary  strainer"  has  been 
used  with  success  in  some  cases,  this  consisting  of  a  revolving 
cylindrical  screen  at  the  mouth  of  the  suction,  which  is 
caused  to  rotate  by  air  forced  to  it  from  the  shore,  as  above. 

An  intake-pipe  or  tunnel  leads  from  the  intake  to  a 
suction-well,  from  which  the  water  is  pumped;  or  the  pipe 
may  act  as  a  suction-pipe  and  lead  direct  to  the  pump,  this 
being  the  common  arrangement  for  small  plants.  The  Mil- 
waukee water-works  intake-conduit  consists  of  a  tunnel  3000 
feet  long,  continued  further  into  the  lake  by  two  lines  of 
60-inch  pipe  5000  feet  long  laid  in  an  8~foot  trench  and 
terminating  in  60  feet  of  water.  Chicago  and  other  large  lake 
cities  also  take  their  supply  through  tunnels;  but  smaller 
supplies  are  generally  drawn  through  pipes,  either  cast  or 
wrought  iron,  laid  in  the  bed  of  the  stream  or  lake.  These 
should  be  laid  in  trenches,  to  protect  them  from  currents  or 


DESIGNING.  393 

shifting  sands,  and  are  sometimes  covered  with  rip-rap  as  a 
further  protection. 

If  filter-cribs  are  used  (Art.  79),  these  take  the  place  of 
intake-cribs  (see  Fig.  43).  The  intake-pipe  is  similar  to  that 
from  an  ordinary  crib. 

Art.  92,     Details  of  Ground-water  Plants. 

Except  where  artesian  wells  flow  under  considerable  head, 
it  is  generally  desirable  to  be  able  to  draw  down  the  ground- 
water as  low  as  possible  in  the  well,  thus  increasing  the  flow. 
Since  pumps  can  raise  water  by  suction  only  20  to  25  feet 
with  any  efBciency,  it  is  frequently  necessary  to  lower  the 
pump  to  meet  these  conditions.  If  the  water  rises  to  within 
five  or  ten  feet  of  the  surface,  a  surface-pump  may  be  used, 
placed  in  a  pump-pit  as  described  in  the  previous  Article. 
The  construction  of  this  pit  must  be  such  as  will  exclude  any 
ground-water. 

If  it  is  desired  to  draw  the  water  down  to  a  distance  of 
more  than  40  or  50  feet  below  the  surface,  requiring  a  pit 
more  than  20  or  25  feet  deep,  such  construction  is  not  often 
employed,  but  deep-well  pumps  (Plate  XVII,  page  397)  are 
lowered  into  the  wells.  An  exception  to  this  is  the  Rockford, 
111.,  plant  (see  Fig.  53,  page  349),  where  centrifugal  pumps  are 
used  in  a  pump-pit  80  feet  deep.  The  air-lift  is  in  some  cases 
used  in  place  of  a  deep-well  pump ;  but  the  efficiency  of  both  of 
these  is  so  much  lower  than  that  of  a  good  reciprocating  pump, 
and  the  latter  is  so  much  more  accessible  for  repairs,  that  its 
use  is  recommended  wherever  possible  in  any  but  very  small 
plants,  and  may  be  the  most  economical  in  many  of  these. 
Where  a  large  dug  well  is  the  means  of  supply,  the  pump 
may  be  placed  in  this,  the  boiler  being  on  the  surface,  and 
the  whole  roofed  over.  This  is  likely  to  cause  a  pollution  of 
the  water,   however,   and   a  better  plan   in   most  cases   is  to 


394  WATER-SUPPLY  ENGINEERING. 

place  the  pumping-station  near  the  well,  connecting  the  two 
by  a  suction-pipe,  and  roofing  over  the  well. 

If  the  wells  are  tube-wells,  they  are  ordinarily  coupled  to 
a  main  collecting-pipe  which  passes  by  and  near  them,  the 
short  connecting  branches  being  furnished  with  valve-gates, 
that  any  well  may  be  put  into  or  out  of  service.  Collecting- 
pipe  and  branches  should  all  be  -perfectly  air-tight — a  result 
often  difficult  of  attainment. 

In  spite  of  all  efforts  some  air  is  likely  to  leak  into  the 
collecting-pipe,  and  this  should  be  removed  in  some  way; 
especially  if  the  collecting-pipe  be  connected  directly  to  the 
pumps,  as  the  presence  of  air  in  the  pumps  will  cause  them 
to  '*  pound."  The  only  practical  method  of  accomplishing 
this  seems  to  be  to  place  an  air-drum  in  the  pipe  at  its 
highest  point,  and  remove  the  air  from  this  with  a  vacuum- 
pump.  At  a  plant  of  forty-five  wells  and  5806  feet  of 
suction-pipe  in  Lowell,  Mass.,  two  duplex  vacuum-pumps, 
one  6  X  8^  X  6  inches,  the  other  7^^  X  loj  X  10  inches, 
were  found  necessary  for  this  purpose  in  1894. 

The  pump  may  be  connected  to  the  collecting-pipe  and 
draw  directly  from  the  wells;  in  which  case  a  sand-box  or 
sand-interceptor  should  be  placed  between  the  pump  and  the 
wells  to  prevent  sand  from  entering  and  cutting  the  pump- 
valves  and  plunger  or  piston.  In  a  few  cases  the  pump  draws 
from  a  suction-well  which  has  been  dug  to  somewhat  below 
the  depth  to  which  it  is  desired  to  lower  the  ground-water, 
the  collecting-pipe  being  laid  at  about  the  level  of  the  pump, 
and  its  vertical  end  carried  down  to  near  the  bottom  of  the 
suction-well.  By  this  plan  the  water  is  siphoned  into  the 
suction-well,  which  also  acts  as  a  small  reservoir  to  permit  of 
higher  rates  of  pumping  for  short  intervals  than  could  be 
obtained  directly  from  the  wells.  The  suction-well  also 
serves  to  intercept  the  sand.  The  collecting-pipe  is  apt  to  fill 
with  air  at  its  highest  point,   and   this   should  be    near  the 


DESIGNING.  395 

pumps  and  provided  with  an  air-drum,  and  arrangements 
made  for  removing  the  air  at  intervals. 

The  distance  by  pipe  from  the  pump  to  any  well  should 
be  as  short  as  possible,  and  the  collecting-pipe  of  such  size 
that  the  velocity  of  flow  in  it  shall  not  be  greater  than  2  or  3 
feet  per  second,  that  the  friction  loss  between  well  and  pump 
may  be  a  minimum.  The  best  arrangement  for  obtaining 
this  result  is  to  place  the  wells  in  a  straight  line  at  right  angles 
to  the  direction  of  ground-flow,  pass  the  collecting-pipe  about 
3  feet  from  each  of  these,  and  place  the  pump  at  the  middle 
of  the  collecting-pipe.  If  two  or  more  water-bearing  strata 
are  tapped  by  the  wells,  these  may  all  be  connected  to  one 
collecting-pipe;  but  if  the  water  rises  naturally  much  higher 
from  one  stratum  than  from  another,  it  is  better  to  provide  a 
separate  suction  from  each,  and,  if  more  than  one  pump  is 
used,  so  arranged  that  either  pump  can  draw  wholly  from 
either  stratum  or  from  both  combined. 

If  deep-well  pumps  are  used  one  must  be  placed  in  each 
well,  and  be  driven  by  separate  engines  or  working-heads. 
This  will  require  a  building  of  some  kind  over  each  well;  and 
either  an  engine  to  each  pump,  or  one  engine  transmitting 
its  power  by  rope,  belt,  water-  or  air-pressure,  or  electricity 
to  the  various  working-heads.  For  this  reason  deep  non- 
artesian  wells  should  be  given  large  casings  and  powerful 
pumps,  that  their  number  may  be  reduced  to  the  minimum. 

The  location  of  wells  has  already  been  referred  to.  It  is 
generally  desirable  to  drive  them  on  low  ground,  as  the 
suction-lift  of  the  pumps  is  thus  reduced  at  the  least  expense 
of  pump-pit  excavation.  They  should  never  be  placed  along 
the  direction  of  ground-water  flow,  but  as  nearly  as  possible 
at  right  angles  to  it.  The  most  desirable  spacing  will  vary 
with  the  material,  volume  of  flow,  and  depth  to  which  pumps 
lower  the  water  in  the  well,  and  can  be  learned  for  each  case 
only  by  trial.      It  should  generally  be  such  that  the  ordinary 


39^  WATER-SUPPLY  ENGINEERING. 

pumping  of  one  well  will  have  little  effect  upon  the  simul- 
taneous yield  of  its  neighbors.  This  is  particularly  true  o'" 
deep  and  expensive  wells.  At  Galveston,  Tex.,  thirty  7-inch. 
and  9-inch  wells,  750  to  850  feet  deep,  are  located  at  inter- 
vals of  300  to  750  feet.  The  sinking  of  an  additional  well 
between  any  two  others  will,  however,  almost  always  increase 
the  total  supply,  although  it  may  be  but  slightly;  and  if  the 
wells  are  shallow  and  cheaply  driven  they  may  be  placed 
quite  close  together.  At  the  Spring  Creek  Station  of  the 
Brooklyn  water-works,  one  hundred  2-inch  wells,  30  to  42 
feet  deep,  are  placed  in  two  rows  14  feet  apart,  the  interval 
along  each  row  also  being  14  feet;  and  the  same  spacing  is 
used  at  the  Jameco  Station,  where  are  one  hundred  and 
eighty-three  2-inch  wells  from  27  to  73  feet  deep. 

Each  driven  well  is  furnished  with  a  strainer  which  is 
several  feet  in  length;  in  deep  wells  this  length  may  equal 
the  thickness  of  the  water-bearing  stratum ;  in  shallow  wells 
it  usually  occupies  the  lowest  3  or  4  feet  only.  The  strainer 
is  a  section  of  wrought-iron  pipe  pierced  with  holes  or  slits 
to  admit  the  water,  and  generally  covered  with  a  gauze  screen 
to  exclude  sand  and  gravel.  The  gauze  should  be  protected 
by  a  heavy  screen  or  thin  tube  of  pierced  metal  surrounding 
it  called  a  jacket.  Probably  the  best  strainer  for  sand  is  the 
Cook,  which  is  formed  by  vertical  or  horizontal  slits  cut  as 
shown  in  Plate  XVII,  a.  At  b  is  shown  a  drive-well 
"  point,"  and  a  strainer  before  the  gauze  and  jacket  are  put 
on;  and  at  <:  is  a  point  and  strainer  with  which  no  gauze  is 
used.  Points  are  used  when  the  well  is  driven  into  the 
ground  by  blows  of  a  heavy  hammer  (called  a  drive-well). 
An  open-foot  well  is  "washed  down  "  by  forcing  water  into 
it  and  thus  washing  to  the  surface  the  soil  beneath  the  pipe, 
which  is  forced  down  simultaneously. 

In  Plate  XVII  is  shown  a  deep  well  with  strainer  and 
deep-well  pump.      At  the  top  is  shown  the  engine,   to  the 


DESIGNING. 


397 


Plate  XVII. — Deep  Well,  with  Pump  ;  and  Strainers. 


398 


IVATER-SUPPLY  ENGINEERING. 


right  of  which  is  an  air-chamber  on  the  pumping  main  for 
reducing  the  water-hammer  due  to  the  intermittent  action  of 
the  single-acting  pump.  At  B  is  the  pump-barrel,  which  is 
fastened  in  the  bottom  of  the  well-tubing,  and  is  provided  at 
Z^  with  a  valve.  At  6'isa  piston  and  valve,  which  is  raised  and 
lowered  by  the  pump-rod  connecting  with  the  engine-piston. 
A  dug  well  is  generally  circular  with  brick  or  stone- 
masonry  walls,  as  shown  in  section  in  Fig.  (>6\  but  a  some- 
what greater  interception  of  ground-flow  and  ease  of 
construction   may  be  obtained  with  a  long  well  of  the  same 


VERTICAL   SECTION 


CIRCULAR    WELL 


•m^ 


7//,^M^^imiA;''''-^C-r-.^-^-  '...v.:i*i? 


Fig.  66. — Deep  Dug  Wells. 

storage-capacity;  although  more  masonry  will  be  required. 
Such  a  well,  which  was  sunk  to  a  depth  of  32  feet,  is  shown 
in  plan  in  Fig.  G^. 

Infiltration  cribs  and  galleries  are  practically  elongated 
deep  wells  roofed  over  below  the  surface.  Timber  ones  are 
ordinarily  made  on  the  general  plan  shown  in  Fig.  6"].  They 
should  be  used  only  where  the  entire  crib  is  always  immersed, 
as  otherwise  they  are  liable  to  decay.  A  masonry  gallery 
may  be  made  in  the  form  of  a  circular  sewer,  with  a  great 


DESIGNING. 


399 


number  of  openings  left  in  the  walls;  or  may  have  vertical 
walls  and  an  arched  top,  the  bottom  being  open  to  admit  the 
water.      Infiltration  galleries  and  cribs  generally  lead  directly 


Fig.  67. — Infiltration-crib,  Denver  Water-works. 

(From  Trans.  Am.  Soc.  C.  E.,  Vol.  XXXI.) 

to  or  are  connected  by  pipe  with  a  suction-well,  from  which 
the  water  is  pumped.  They  may  be  extended  from  time  to 
time  as  the  demand  increases,  always  crossing  the  line  of 
ground-flow  approximately  at  a  right  angle.  A  manhole 
should  be  provided  to  give  access  for  repairs  and  cleaning. 

Art.  98.     Details  of  Purification  Plants. 

Mechanical  filters,  being  patented  articles,  are  furnished 
and  set  ready  for  service  by  the  company  contracting  for 
them.  The  contract  should  stipulate  the  service  to  be  per- 
formed, such  as  the  maximum  percentage  or  amount  of 
mineral  and  organic  matter  and  bacteria  which  shall  pass  the 
filter  at  any  time,  during  a  certain  maximum  rate  of  filtration. 
It   is  generally  desirable  to  place   mechanical  filters  in   one 


400  WATER-SUPPLY  ENGINEERING. 

room  of  the  pumping-station,  that  the  pump-engineer  may 
keep  them  under  his  immediate  supervision.  Pressure  filters 
are  conveniently  located  near  the  pumps,  being  interposed  in 
the  pumping-main.  Gravity  filters  may  be  placed  on  a  level 
with  or  even  a  little  above  the  main  pumps,  and  should 
discharge  into  a  sruction-well.  The  water  can  in  some  cases 
be  brought  to  the  gravity  filters  by  a  flume  or  a  short  race,  as 
from  above  a  river-dam,  but  must  generally  be  pumped. 
The  lift  will  ordinarily  be  light,  and  as  the  rate  of  filtration, 
and  consequently  of  pumping,  should  be  uniform,  and  the 
water  may  be  muddy,  centrifugal  pumps  are  well  adapted  to 
this  service.  For  pressure  filters  both  the  pump-room  and 
filter-room  could  be  smaller,  since  no  intake-pumps  and  fewer 
filters  would  be  required. 

All  steam-  and  water-piping  should  be  so  arranged  that 
any  boiler  could  be  used  for  running  any  pump;  that  any  or 
all  pumps  could  be  put  in  or  out  of  service  instantly;  and 
that  any  filter  could  be  put  in  or  out  of  service,  or  be  cleaned, 
without  interfering  with  the  others;  also  a  by-pass  around 
the  filters  should  be  provided,  to  be  used  for  the  occasional 
imperative  demands  of  the  fire  department.  All  the  rooms 
may  be  upon  the  same  level,  the  suction-well  being,  of 
course,  lower.  If  sedimentation-basins  are  used,  these  may 
be  so  placed  that  water  from  the  river  (generally  the  only 
kind  requiring  sedimentation)  can  flow  directly  into  them,  and 
the  pumps  draw  from  these;  or  they  may  be  at  such  an 
elevation  that  their  effluent  can  flow  directly  into  the  filters, 
if  these  are  the  gravity  type,  the  water  being  lifted  from  the 
river  to  them  by  intake-pumps,  as  above;  or  it  may  be 
necessary,  in  the  case  of  gravity  filters,  to  provide  special 
pumps  to  raise  water  into  the  basins  and  from  them  into  the 
filters.  Probably  the  best  plan,  when  sedimentation  is 
necessary,  is  to  use  pressure  filters,  and  to  place  the  basins 
level  with  the  river  if  possible. 


DESIGNING.  401 

A  sedimentation-basin  is  practically  but  a  small  reservoir, 
and  is  constructed  as  such.  When  it  is  desired  to  provide  a 
number  of  basins  (see  Art.  y6)  this  is  generally  accomplished 
by  dividing  up  the  reservoir  by  a  number  of  partition-walls. 
The  dimensions  of  these  are  fixed  by  the  rules  for  masonry 
dams,  the  vertical  section  being  either  rectangular  or  trape- 
zoidal, and  the  top  width  two  or  three  feet.  It  is  desirable 
to  arrange  for  conveniently  cleaning  the  basins,  and  disposing 
of  the  sediment.  For  this  purpose  a  traveller,  spanning  one 
basin  and  running  upon  tracks  fixed  on  the  partition-walls, 
from  which  buckets  can  be  raised  and  lowered  in  any  part  of 
any  basin,  is  often  an  economical  contrivance  when  the  basins 
are  narrow.  If  there  is  little  sediment,  however,  or  if  the 
basins  are  large,  no  fixed  appliance  is  generally  provided,  the 
material  being  removed  by  wheelbarrows  on  temporary  plank 
runways. 

English  filters  have  been  formed  by  placing  the  filtering 
material  in  the  bottom  of  old  reservoirs;  and  new  ones  are 
commonly  made  similar  to  a  reservoir  8  to  12  feet  deep. 
The  general  construction  of  these  filters  has  already  been 
described  in  Art.  JJ.  Particular  pains  should  be  taken  to 
properly  grade  the  materials  from  coarse  to  fine,  and  so 
compact  them  all  that  no  considerable  settlement  may  take 
place,  and  that  the  sand  be  not  washed  through  into  the 
drains.  The  sand  must  be  of  uniform  size  throughout  each 
layer  of  each  filter  to  insure  a  uniform  rate  of  filtration  in  all 
parts  of  the  same.  Water  should  be  so  admitted  to  the  filter 
as  to  prevent  washing  of  the  sand  near  the  inlet;  which 
requires  a  very  low  velocity  in  the  inflowing  water,  such  as  a 
steady  flow  over  a  long  weir.  In  the  Albany  plant  this  is 
effected  by  a  weir  in  the  form  of  a  quarter-circle,  shown  at  ^, 
Fig.  I,  Plate  XVIII.  In  the  same  figure  is  shown  the 
arrangement  of  drains  and  collectors,  the  right-hand  half 
showing  the  manholes  in  the  roof.     The  construction  of  the 


402 


WA  TER-SUPPL  Y  ENGINEERING. 


tS±_° 

REGULATOR 
CHAMBE: 


SECTIONAL  PLAN,  SAND  REMOVED. 


SECTIONAL  PLAN  AT  EL.  1  19.0 


\F"  r^nr^'j'^r^^^^     ^■•_\y 


-V;5!5;^ 


W;-i»-;^<--fa5Tr 


_M  ri""!' M I  i^rTTTriTTfrnnnTfTiiT 


LONGITUDINAL  SECTION  PLAN  AND  SECTIONS 

10  20  30  40         50   PART  OF  FILTER  NO.  2  OR  6 


SCALE  OF  FEET 


2^___   __ ^_  LOAM      rq     V"'"^ — ^ 


h-2lH 

/^     / 

^■^FV 

/ 

^^ 

-x-^ 

,   f 

■»- 

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w 

./.... 

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COLLECTOR 


f0  SECTION  THROUGH  MANHOLES. 

Plate  XVIII. — Albany  Filter-beds. 


DESIGA'ING.  403 

roof  and  drains  is  shown  more  plainly  in  Fig.  2,  and  the 
arrangement  of  filtering  materials  in  Fig.  41,  page  299.  In 
Plate  XIX,  Fig.  i,  is  shown  the  general  arrangement  of  the 
filter-beds  and  sedimentation-basin.  Water  from  the  river 
enters  at  d,  and  passes  either  to  the  right  and  into  the  basin 
through  the  inlets  c,  c,  or  directly  to  the  beds  through  the 
36-inch  pipe  at  the  left  and  lower  side  of  the  basin,  entering 
the  beds  through  the  inlets  a,  a.  Water  from  the  sedimen- 
tation-basin passes  through  the  outlets  /,  f  to  the  36-inch 
pipe  just  referred  to,  and  thence  to  the  beds. 

The  height  of  water  on  the  beds  is  controlled  by  the  float 
and  valve  at  a  (the  same  letters  are  used  in  both  plates  for 
corresponding  parts),  and  is  prevented  from  rising  above  a 
given  height  by  overflows  at  c,  c\  at  which  point  also  the 
water  may  all  be  drawn  off  the  beds,  water  from  the  overflow- 
chambers  being  wasted.  The  rate  of  filtration  is  controlled 
at  the  regulator-chambers  b,  b.  Between  the  two  sets  of 
beds  is  a  court  in  which  is  the  laboratory  and  sand-washer, 
the  sand  being  removed  by  a  runway  in  each  bed.  The  filter 
effluent  flows  to  a  pure-water  reservoir. 

For  smaller  plants  the  arrangements  are  generally  more 
simple,  but  the  general  plan  should  be  practically  the  same. 

If  it  is  desired  to  filter  the  water  of  a  surface  supply, 
similar  filters,  either  slow  or  mechanical,  may  be  placed 
between  the  storage-  and  distributing-reservoirs,  gravity 
pressure  only  being  used.  A  distributing-reservoir  is  neces- 
sary when  a  supply  is  filtered,  since  a  filter  should  work  at  a 
uniform  rate  while  the  consumption  is  not  uniform.  It  is 
desirable  to  cover  this  reservoir,  to  preserve  the  purity  of  the 
filtered  water.  The  storage-reservoir  will  generally  act  as  a 
sedimentation-basin,  and  a  special  basin  for  this  purpose 
will  be  unnecessary. 

A  by-pass  from  river  or  storage-reservoir  around  the  filter- 
basin  should  be  provided,  for  occasional  use.      It  may  in  some 


36'  30'   SUPPLY    PIPE    FROM    2t'   , ,  l""^"  , ,      20 


36  30      SUPPLY    PIPE     PROM     ;;>  HIVEH  'J) 


SEDIMENTATION    BASIN 


It-..- 
Ji   , 

I    i-17.26 


-665:50 — 


Sz  OUTLET  pIpES      J;fo5 


I    j  LABORATORY  Ji      """-■"  -"psv^iT-aa ;    I 

' b?iTTTiTnTnTri7T^  t¥  irrrrTrmiTrTrniTi'^ 


COMPACTED  EARTH 

Fig.  2 

Plate  XIX. — Albany  Filter-beds. 

Fig.  I. — Sedimeniaiion-basin  and  Pipe  Systems. 

Fig.  2. — Bank,  and  Inlet  and  Outlet  Pipes  of  Sedimentation-basin. 


DESIGNING.  405 

cases  be  found  that  filtration  is  necessary  only  a  part  of  the 
time,  the  water  being  used  unfiltered  during  the  remainder. 
This  is  often  the  case  with  surface-waters  in  which  the  only 
objectionable  impurity  is  the  occasional  presence  of  algae  in 
large  numbers,  or  clay  or  loam  washed  in  by  heavy  rains. 

Art.  9-i.     Details   of   Conduits   and   Distribution 

Systems. 

Canals  embody  the  same  principles  of  construction  as  dft 
earth  dams  and  reservoirs.  The  side  slopes  are  generally 
\\  to  I,  the  tops  of  embankments  6  to  12  feet  wide.  The 
same  precautions  and  means  are  taken  to  prevent  leakage. 
Earth  canals  are  seldom  used  for  city  supply;  but  for  irriga- 
tion systems  have  been  used  both  with  and  without  lining. 

On  the  Santa  Ana  Canal  (California)  one  section  is  in 
clay,  having  a  top  width  of  12^  feet  and  a  depth  of  7^  feet, 
the  sides  being  sloped  but  ^  to  i,  the  bottom  being  rounded 
and  the  whole  lined  with  stone  in  cement-mortar,  and  given 
a  coating  of  rich  cement-mortar;  the  walls  being  about 
6  inches  thick  at  the  top  and  12  to  15  inches  at  the  bottom. 
Plate  VIII,  page  175,  shows  a  section  of  this  canal. 

Canals  with  masonry  walls  may  be  used  with  satisfaction 
where  bed-rock  is  found  at  the  surface.  This  will  generally 
be  on  the  side  hills,  where  the  canal  will  be  formed  on  a 
bench.  The  rock  will  then  form  the  bottom  and  usually  one 
side,  and  the  other  side  is  formed  by  a  masonry  wall,  the 
stone  for  which  is  obtained  in  the  excavation.  The  wall 
should  be  at  least  two  or  three  feet  thick  on  top,  and  of 
trapezoidal  section.  It  is  better  to  use  small  "  one-man  " 
stones,  laid  in  rich  cement-mortar  thoroughly  filling  all  joints. 
If  the  work  is  at  all  seamy  or  porous,  the  canal  should  be  lined 
with  concrete  and  given  a  cement  coating. 

The  most  common  form  of  open  conduit   is  the   flume, 


4o6 


WATER-SUPPLY  ENGINEERING. 


made  wholly  or  partly  of  timber.  The  rectangular  flume  is 
illustrated  in  Plate  X,  page  179;  its  general  construction  is 
shown  in  Fig.  68.     A  tighter  and  more  durable  flume,  known 


Fig  68. — Box-flume  Construction. 
as  the  stave  and  binder  flume,  has  been  used  recently  in  the 
West.  Its  general  construction  is  shown  in  Fig,  69.  In  this 
the  bottom  is  made  like  the  lower  half  of  a  wood-stave  pipe, 
but  vertical  sides  take  the  place  of  a  closed  top;  a  binding- 
rod  passes  around  the  flume,  its  ends  passing  through  the  two 
ends  of  a  cross-head  and  being  provided  with  nuts  by  which 
the  staves  are  forced  together.  This  flume  is  supported  by 
stiff  U-shaped  frames  of  T  iron  resting  on  wooden  bolsters 
or  sills  and  spaced  8  feet  apart,  each  frame  resting  on  con- 
crete foot-blocks. 

Flumes  resting  on  benches  should  be  supported  wholly 
by  the  original  soil,  and  in  no  place  by  filling.  The  sills 
should  be  raised  above  the  ground  a  short  distance  and 
supported  on  solid  stone,  brick,  or  concrete  foot-blocks.  The 
excavation  should  be  carried  into  the  hillside  three  or  four 
feet  beyond  the  flume,  to  lessen  the  danger  of  this  being 
damaged  by  stones  or  earth  falling  from  above.  The  timber 
used  should  be  that  which  is  least  liable  to  decay. 

Creosoting  will  add  considerably  to  the  life  of  the  timber, 
but  is  generally  too  expensive.  If  all  surfaces  intended  to 
come  in  contact  are  first  painted  with  hot  asphaltum  or  tar, 
decay  will  be  considerably  delayed. 


DESIGNING. 


407 


408 


WA  TEK-SUPPL  Y   ENGINEERING. 


A  closed  conduit  may  be  made  by  covering  a  timber  flume 
with  plank,  or  may  be  constructed  of  masonry.  The  latter 
plan  is  generally  adopted,  and  the  conduit  is  covered  virith  a 
few  feet  of  earth  to  protect  it  from  frost  in  winter  and  heat  in 
summer,  and  from  malicious  damage.  It  is  generally  circular 
in  section  when  in  firm  soil,  this  shape  being  the  most  eco- 
nomical. It  may  be  made  of  brick,  stone,  or  concrete.  If  of 
brick,  two  concentric  rings  are  generally  employed  up  to  a 
diameter  of  about  5  feet;  three  rings  up  to  about  10  feet. 
When  on  the  surface,  on  a  timber  or  other  foundation,  or  in 
unstable  soil,  the  "  horseshoe  "  section  is  ordinarily  employed, 
having  an  arched  top,  vertical  side  walls  sufficiently  heavy  to 
receive  the  thrust  of  this,  and  a  flat  inverted  arch  at  the 
bottom.  Such  a  section  is  shown  in  Fig.  70,  that  of  the 
old  Croton  Aqueduct.  Vertical  side  walls  of  an  aqueduct  are 
generally  made  of  stone  masonry,  lined  with  brick  or  concrete. 


Fig.  70. — Old  Croton  Aqueduct. 
The  foundation  of  a  masonry  conduit  or  aqueduct  must 
be  absolutely  rigid,  since  the  least  settlement  and  crack  in  the 
aqueduct  may  lead  to  serious  results.  To  prevent  softening 
of  the  supporting  soil,  as  well  as  waste,  the  masonry  should 
be   water-tight.      The   Wachusett,    Mass.,    Aqueduct    where 


DESIGA'/XG. 


409 


crossing  a  valley  on  a  masonry  bridge  is  rendered  water-tight, 
in  spite  of  any  slight  settlement  of  the  bridge  arches,  by 
lining  the  channel  with  sheet  lead  weighing  5  lbs.  to  the 
square  foot,  and  protecting  this  from  wear  by  an  inside  layer 
of  brick. 


IN  LOOSE  EARTH 


IN  COMPACT  EART 


IN  ROCK 

Fig.  71. — Sections  of  Concrete  Aqueduct. 
(Nashua  Aqueduct,  Metropolitan  Water-supply.) 

Conduits  under  pressure  cannot  be  built  of  masonry; 
except  that  concrete  has  been  so  used  when  having  imbedded 
in  it  "  expanded  metal,"  heavy  screens,  or  iron  rods  both 
longitudinal  and  encircling  the  aqueduct,  to  sustain  the 
tension.     The  majority  of    pressure   conduits,   however,   are 


41 0  WATER-SUPPLY  ENGINEERING. 

made  of  cast  or  wrought  iron  or  steel,  or  of  wood,  either  as 
bored  logs  or  stave-pipe.  In  the  metal  pipes  the  tension  is 
resisted  by  the  cohesion  of  the  material  itself.  Bored  logs 
exert  this  to  a  certain  extent;  but  if  to  sustain  much  pressure, 
they  are  tightly  wrapped  with  wire  or  iron  bands.  Stave- 
pipes  rely  entirely  upon  iron  bands  or  hoops  for  their  resist- 
ance to  internal  pressure;  except  that  between  these  the 
stiffness  of  the  staves  prevents  springing  and  leaking. 

The  pressure  to  be  resisted  by  a  pipe — that  is,  the 
resultant  component  of  all  forces  in  any  one  direction  in  its 
cross-section — equals  WhdL,  in  which  IV  is  the  weight  of  a 
cubic  foot  of  water,  d  is  the  diameter  of  the  pipe  in  feet,  //  is 
the  head  upon  the  centre  of  the  pipe,  and  L  is  the  length  of 
pipe  considered.  If  we  make  L  one  inch,  and  express  d  in 
inches,  making  IF  the  pressure  upon  a  square  inch  due  to  one 
foot  head,  the  internal  pressure  /*=  .434//^/ lbs.  per  lineal  inch. 
This  is  resisted  equally  (in  a  circular  pipe)  by  both  sides,  and 

.434/^^/ 
hence  the  tension  per  square  mch  of  metal  T  =■ — ,  in 

which  t  is  the  thickness  of  the  shell  in  inches,     h  must  be 

taken  as  the  maximum  head  possible,  including  that  due  to 

water-hammer;  and  a  sufificient  factor  of  safety  must  be  used, 

which  will  vary  with  the  substance  employed.     A  minimum 

thickness  must  be  adopted,  below  which  the  pipe  would  be 

subject  to  distortion  or  breakage  by  handling.      If  we  allow 

200  lbs.  for  water-ram  (see  Fig.  23),  and  call  s  the  ultimate 

tensile  strength  of  the  substance  used  and  F  the  factor  of 

(.434/^  -(-  20o)dF 
safety,  the  formula  for  thickness  will  be  /  = . 

This  lormula  does  not  apply  to  pipe  where  the  tension  is 
sustained   by   bands.      In   these    P  ■=  .^l\hd  lbs.    per    lineal 

.  .^I4.hdh 

inch,  and  the  tension  in  each  rod  is ■,  in  which  h  is  the 

'  2 

distance  between  bands  in  inches.  This  tensile  strain  is  of 
course  acting  in  every  part  of  the  pipe  or  band. 


DESIGNING. 


411 


for  4-inch  diameter f 

for  8-inch  diameter -^^ 

for  lo-inch  diameter ^  in. 

for  16-inch  diameter \ 

for  20-inch  diameter i 


nch  diameter ii '"• 

nch  diameter fin. 

nch  diameter to  ''^« 

nch  diameter 1  in. 


The  minimum  limit  for  cast-iron  pipe  may  be  taken  to  be: 

for  24- 
for  30- 
for  42- 
for  48-i 
for  60-inch  diameter i^^  in. 

The  tensile  strength  of  ordinarily  good   cast  iron  may  be 

generally    taken    at     18,000    lbs.    per    square    inch.       Many 

formulas  have  been  advanced   for  determining  the  thickness 

of  pipe,  allowing  for  minimum  thickness  and  tensile  strength. 

That  of  James  B.  Francis  is 

t  =  .000058M4-  .01 52c/ -f  -312  {t  and  d  in  inches, 

Ji  in  feet). 

/  =  .oooo6/z<:/-|-  .oii^^dAr  .296 

is  used  by  the  Warren  Foundry  and  Machine  Company.  Cast- 
iron  water-pipes  are  ordinarily  connected  by  hub-and-spigot 
joints,  filled  with  melted  lead  which  is  "  set  up  "  with  calking- 
tools.  For  indoor  work,  joints  which  it  is  desired  to  unmake 
occasionally,  and  some  other  conditions,  flanged  pipe  is  used, 
but  is  not  desirable  for  underground  work  because  of  its 
inflexibility,  and  is  more  expensive  than  the  hub-and-spigot 
joint.  The  flanges  of  flanged  joints  are  faced  down  to  a 
true  plane  at  exact  right  angles  to  the  axis  of  the  pipe ;  and 


^vO.25' 


Fig.  72. — Joints  of  Cast-iron  Pipe. 
in  joining  them   a  ring  of  packing — sheets   of  rubber    and 
cotton,  corrugated  copper,  lead  wire,  and  other  materials  are 
used,  the  first  being  the  most  common — is  placed   between 
the  flanges,  which  are  drawn  tigliHy  together  by  bolts. 


412 


WA  TEK-SUPPLY  ENGINEERING. 


The  New  England  Water-works  Association   has  recently 

adopted  a  standard  for  water-pipe,  which  it  is  hoped  will  come 

into  general  use.      The  upper  part  of  the  hub  and  spigot  joint 

in  Fig.  72  shows  this  standard,  and  the  dimensions  are  given 

in  the  follow  table: 

Table  No.   69. 

n.  e.  w.  w.  assn.  standard  dimensions  and  weights  of 
cast-iron  water-pipe. 


u 

Diameter 

De 

pth 

u 

of 

0 

i 

i 

'O 

Soc 

kets. 

Soc 

kets. 

3  s 

b. 

Thickness  o 
Shell. 

f 

Weifi 

(5 

«•■ 

^ 

a. 

ht  per  Length. 

Ot5 

2  n! 

b« 

Clio 

c 

<j 

^  c 

_  c 
2  " 

a 
0 

5^ 

u 

'p  !S 

<j 

u  rt 

a 

t;Q 

a 

S.U 

a. 

S!; 

0 

< 

0^ 

</) 

oH 

1i 

Ins. 

Ins. 

Ins. 

Ins. 

Ins. 

Ins. 

I 

riches. 

Pounds. 

4 

A,  C,  E 

4.80 

5.60 

5.70 

3.00 

4.00 

.-50 

1 .30 

•34, 

36, 

-39 

200, 

215,    ».3o 

G,  I,  K 

5.00'     5.80 

" 

'• 

** 

•42. 

45, 

.48 

250, 

265,    280 

6 

A,  C,  E 
G,  I 

6.90 
7.ro 

7-77 
7.90 

7.80 

'' 

'.1 

'.' 

1.^40 

.38, 
.50, 

.42, 

•54 

.46 

330, 
420, 

350,    380 
445 

8 

A.  C,  E 
G,  I 

9.05 
9-3° 

9.85 
10. 10 

10  00 

3-^50 

.. 

- 

1,^50 

•  4^ 
.58, 

48, 
63 

•53 

475, 
640, 

530,     575 
690 

10 

A,R,C,D 

1 1 .  10 

II  .90 

12.10 

" 

4.^50 

" 

'' 

-47. 

50, 

•53, 

•56 

650, 

680,     720,     760 

" 

E,F,G,H 

11 .40 

12.20 

" 

.60, 

63, 

•  67, 

.70 

810, 

S50,     890,     935 

12 

A,B,e,D 

13.20 

14.00 

14.^21 

^' 

'' 

" 

1 .60 

49, 

53, 

■57, 

.61 

810, 

855,    910,    970 

E.F.G.H 

13-50 

14-30 

" 

'* 

.65, 

69, 

•73, 

•77 

1040, 

1 100,  1 1 60,  1220 

14 

A,B,C,D 

'5-,30 

16.10 

.6.35 

" 

" 

1.70 

-53. 

57, 

.61, 

.66 

1010, 

1080,  1150,  1220 

E,F.G,H 

15-65 

16.45 

'* 

" 

.70, 

75, 

•79, 

.83 

1310, 

1390,  1460,  1530 

16 

A,B,C.D 

17.40 

18.40 

18.60 

4  .^00 

5  00 

1.75 

1 80 

■55, 

60, 

•6S, 

•70 

1215. 

1300,  1390,  1490 

" 

E,F,G,H 

17.80 

18.80 

'■ 

" 

•75, 

80, 

•  85, 

.90 

1610, 

1710,  i8io,  1900 

18 

A,  B 

C,  D 

19.25 
'9-5° 

20.25 

20.50 

20.40 

.' 

i' 

-* 

1 .90 

•57, 
.69, 

63 
75 

1400, 
1660, 

1520, 
1780 

E.  F 

19.70 

20.  70 

20.70 

*' 

" 

'* 

.80, 

86 

1910, 

2040 

20 

A,  B 
C,  D 

21 .30 
21 .60 

22.30 
22.60 

22.50 

^ 

!.' 

- 

"  '°^' 

.60, 
-72, 

66 
79 

1610, 
1920, 

1760 
2090 

E,  F 

21  .go 

22.  QO 

23.00 

" 

** 

" 

.85, 

92 

2260, 

2420 

24 

A,  B 
CD 

25.40 
25.80 

26.  40 

26  a. 

26.60 

" 

li 

-  .^-0 

'.."" 

.64, 
.80, 

72 
88 

2050, 
2550, 

2290 
2780 

E,  F 

26. 10 

27  10 

27.10 

" 

" 

*' 

.05,  I 

03 

3000, 

3240 

^o 

A,  B 

31-60 

32.60 

32.60 

4.50 

" 

2. 30 

-71, 

81 

2860, 

3230 

C,  D 

32 .  00 

33  -  00 

33  00 

*' 

" 

*' 

.qi,  I 

01 

3600. 

3950 

E,  F 

32.40 

38-40 

33.40 

" 

*' 

" 

1 . 10,  I 

20 

434-:i. 

4700 

36 

A,  B 

37  80 

38,80 

38. 80 

" 

" 

" 

2.50 

■79, 

90 

3800, 

4270 

(",  D 

38.30 

39  •  30 

39-30 

" 

*' 

** 

1 .02,  I 

13 

4S40, 

5310 

E,  F 

38.70 

39.70 

39-70 

" 

" 

*' 

^* 

1.25,  I 

37 

5900, 

6400 

42 

A,  B 

44.00 

45.0 

45.00 

5.00 

" 

*' 

2.80 

•  87.1 

00 

4920, 

55fio 

CD 

44-50 

45-50 

-(5-50 

** 

" 

" 

*' 

I. 13,  I 

27 

6270, 

6970 

E.  F 

45.10 

46.10 

46. 10 

" 

" 

** 

** 

I . 40.  I 

53 

7720, 

8360 

48 

A.  B 

50.20 

51 .20 

51    20 

" 

^' 

** 

3.00 

-95,  I 

10 

6130, 

6970 

CD 

50.80 

5 1 .  80 

51.80 

" 

" 

*' 

1 .25,  I 

40 

7920, 

8780 

E,  F 

51-40 

52  -  4r 

52.40 

'* 

*^ 

*' 

^* 

1-55,  I 

70 

9740, 

10600 

54 

A,  B 

56.40 

57-40 

57.40 

5.50 

5.50 

2.25 

3.20 

..03,  I 

20 

75'0, 

8600 

C,  D 

57-'o 

58.  ir 

:8     I. 

■' 

" 

I   37,  I 

54 

9800, 

lOQOO 

E,  F 

57-80 

58.80 

=  S,8o 

*' 

'■ 

" 

3.80 

1 .  72,  I 

90 

12400, 

13500 

60 

A,  B 

62.60 

63  -  60 

6:   "■ 

** 

" 

** 

3.40 

1. 10,  I 

30 

8900, 

10300 

C,  I) 

63 .  4c 

64.40 

'  4--1' 

" 

"■ 

1.50,  I 

70 

11900, 

13300 

E,  F 

64.20 

65 .  20 

65   20 

4.00 

1 .  90,  2 

10 

15100, 

16500 

Cast-iron  water-pipes  are  made  to  lay  12  feet  of  conduit 
each.  Any  i)ranjh  pipe  or  special  constructions  are  connected 
with  i   tby  means    of   special  castings,    or    "specials";    and 


DESIGNING.  413 

valve-gates  are  made  with  bells  or  flanges  similar  to  those  on 
the  pipe,  and  are  interposed  in  the  pipe-line  where  desired. 
The  specials  ordinarily  used  and  kept  as  stock  patterns  are 
shown  in  Fig,  73,  and  their  dimensions  are  given  in  Table 
No.  70.  The  specials  here  shown  have  a  spigot  at  one  end 
and  hubs  at  the  others;  but  they  are  sometimes  made  with 
hubs  at  all  ends.  The  metal  used  in  cast-iron  pipes  should 
be  a  superior  quality  of  gray  iron,  remelted  in  the  cupola  or 
air-furnace,  tough  and  of  even  grain,  and  should  possess  a 
tensile  strength  of  not  less  than  18,000  lbs.  per  square  inch. 
Test-bars  of  the  metal  3  inches  by  \  inch,  when  placed  upon 
supports  18  inches  apart  and  loaded  in  the  centre,  should 
have  a  transverse  breaking-load  of  not  less  than  1000  lbs., 
and  should  have  a  total  deflection  of  not  less  than  f  inch 
before  breaking.  These  test-bars  should  be  poured  from  the 
ladle  at  any  time  the  engineer  directs,  before  or  after  the 
castings  have  been  or  while  they  are  being  poured.  The 
thickness  of  the  shell  of  the  pipe  should  be  uniform  through- 
out, but  it  seems  almost  impossible  to  obtain  exact  compliance 
with  this.  When  one  side  of  the  pipe  is  somewhat  thinner 
than  the  other,  unequal  cooling  causes  internal  strains,  and 
because  of  these  and  the  thinner  metal  it  is  desirable  to 
double  the  factor  of  safety  which  would  be  used  were  the 
shell  of  uniform  thickness  throughout  and  the  weight  of  the 
entire  pipe  still  that  actually  obtained.  A  factor  of  5  to  lO 
is  generally  employed. 

Cast-iron  pipe  will  rust  and,  with  some  classes  of  waters 
passing  through  it,  become  covered  with  tubercles  in  a  few 
years  unless  protected  with  a  coating.  Several  substances 
have  been  tried  for  this,  but  that  which  has  generally  proved 
most  satisfactory  and  is  now  used  by  many  if  not  all  foundries 
is  Angus  Smith's  coating,  which  was  first  used  in  Manchester, 
England,  in  1849,  and  in  this  country  in  the  Brooklyn 
water-works  in    1858,      In  applying  this  coating  the  pipes  are 


414 


WA  TERSUPPL  Y  ENGINEERING. 


immersed   in  a  hot  bath  of  boiling  coal-pitch   from  which  the 
naphtha    compounds    have    been    distilled    off    and    a    small 


SECTION  ON  A  B. 


blow-off  branch 
Fig.  73. — Cast-iron  Pipe  Specials. 


amount  of  mineral  oil  added  to  give  fluidity.  The  pipe 
should  remain  in  this  hot  compound  until  itself  heated,  when 
it  will   have  received  a  tough  adhesive    coat   of    pitch.      No 


DESIGNING. 


415 


cast-iron  pipe  should  ever  be  laid  without  being  first  coated 
with  this  or  an  equally  good  compound. 

Table  No.  70. 
dimensions  of  pipe  specials,  in  inches. 


Bends. 

Crosses 

Tees. 

• 

4J 

go" 

4 

5 

22 

r 

a 

c 

A 

B 

c 

A 

B 

D 

A 

B 

A 

B 

A 

B 

4 

18 

8 

15 

18 

8 

ll 

18 

8 

II 

4 

9 

3 

6 

20 

9 

17 

20 

9 

Si 

20 

10 

13 

5 

II 

4 

S 

22 

10 

20 

22 

10 

10 

22 

12 

14 

6 

12 

4 

10 

24 

II 

23 

24 

II 

Hi 

24 

14 

15 

7 

13 

5 

12 

26 

12 

26 

26 

12 

13 

26 

16 

16 

8 

14 

5 

14 

28 

13 

29 

28 

13 

I4i 

28 

18 

17 

9 

15 

6 

16 

30 

14 

32 

30 

14 

lb 

30 

20 

18 

10 

16 

6 

iS 

32 

15 

35 

32 

15 

i7i 

32 

22 

16 

II 

17 

7 

20 

34 

16 

3H 

34 

16 

19 

34 

24 

20 

12 

iS 

7 

24 

36 

20 

44 

3fa 

20 

22 

38 

28 

22 

14 

20 

8 

Flanged  Branches. 
Crosses,  and  Tees. 

Blow-off  Branches. 

Reducers. 

B 

nS 
C 

A 

B 

a 

b 

c 

d 

Diameters. 

A 

4 
6 

8 

ID 
12 

14 
16 

iS 
20 
24 

15 
18 
21 
24 
27 
30 

33 
36 
39 

45 

1\ 

9 

10^ 
12 
I3i 
15 
16I 
iS 

I9i 
22^ 

8 

10 
12 
16 
20 
24 
30 
36 
40 
48 

4 

4 

4 

4 

6 

6 

12 

12 

12 

16 

10 
10 
10 
10 
12 
12 
13 
13 
13 
24 

7 

8 

10 
12 

14 

16 

20.5 

23-5 

25-5 

29.5 

5  X  4  to  6  X  3 
8  X  6  to  3  X  3 
10  X  8  to  10  X  5 
12  X  10  to  12  X  6 
14  X  12  to  14  X  6 
16  X  14  to  16  X  8 
18  X  16  to  18  X  8 
20  X  18  to  20  X  8 
24  X  20  to  24  X  10 

29 
32 
35 
38 
41 
44 
47 
50 
56 

Cast-iron  pipe  is  now  used  almost  universally  in  this 
country  for  distribution  systems,  and  for  small  reservoir- 
conduits  also.  House-connections  are  made  with  it  at  any 
point  by  tapping  a  hole  in  the  pipe  and  inserting  a  corpora- 
tion cock.  Larger  connections,  such  as  branch  lines,  fire- 
hydrants,  blow-offs,  etc.,  are  made  by  means  of  special 
castings. 


4i6 


WATER-SUPPLY  ENGINEERING. 


Wrought  iron  or  steel  in  thin  plates  is  used  in  several 
ways  for  water-pipe.  A  small  pipe  may  be  made  of  a  single 
plate  whose  edges  are  riveted  together  or  are  lap-welded; 
or  by  winding  a  long  narrow  plate  spirally  and  riveting  or 
welding  the  spiral  lap.  Larger  pipe  is  riveted,  with  lap-  or 
butt-joints,  and  made  in  sections  15  to  30  feet  long,  each 
formed  of  two  or  more  plates;  either  every  second  section  of 
lap-joint  pipe  being  made  smaller  than  the  others  and  fitting 
tightly  into  their  ends,  or  each  end  is  slightly  tapering,  one 
end  forming  the  inside,  the  other  the  outside,  of  a  lap-joint. 
Another    method    of    uniting    the     sheets    recently    used    in 


LAP  JOINT 
LONGITUDINAL  JOINTS 


LAP  JOINTS 

transverse  joints 

Fig.  74. — Wrought-iron  Pipes 


Australia  is  by  the  locking-bar;  a  double-grooved  bar  receiv- 
ing the  edges  of  the  sheet  and  binding  them  tightly  together 
under  hydraulic  pressure.  For  small  pipe  the  lap-weld  is 
most  used;  and  for  large,  the  riveted  lap-joint.  The  pipe 
is  generally  made  in  15-  to  30-foot  sections  in  the  shop,  and 
these  riveted  together  in  the  field.  For  convenience  of 
joining,  small  wrought-iron  pipe  is  frequently  furnished  with 
a  cast-iron  bell  at  one  end  and  a  narrow  strap  for  a  bead  at 
the  other,  the  pipe  being  joined  with  lead  as  is  cast  iron. 
Most  small  lap-weld  pipe,  however,  is  joined  by  screw 
couplings.  An  expansion-joint  for  connecting  wrought-iron 
pipe  has  been  made  by  giving  each  end  an  outward-flaring. 


DESIGNING.  417 

bell-shaped  flange,  the  advantages  claimed  for  it  being  that 
the  expansion  and  contraction  of  the  pipe  does  not  strain  the 
riveted  joints,  and  that  the  field-riveting  of  joints  can  be 
done  entirely  from  the  outside  with  a  hydraulic  riveter. 

Wrought-iron  or  steel  pipe  is  made  much  thinner  than 
cast  iron,  both  because  the  tensile  strength  of  the  metal  is 
greater  and  because  it  can  be  made  more  uniform  in  character 
and  thickness  of  metal  and  can  be  carefully  inspected  in  the 
sheet.  Also  much  lighter  pipe  can  be  handled  without 
danger  of  breaking.  The  thickness  is  determined  as  for  cast 
iron,  but  a  lower  factor  of  safety  is  used.  Because  of  the 
thinness  of  the  metal  this  pipe  rusts  through  much  more 
quickly  than  cast  iron,  and  hence  a  protective  coating  is  even 
more  necessary.  Large  wrought-iron  or  steel  pipe  is  distorted 
by  the  weight  of  the  back-filling,  unless  the  earth  against  the 
bottom  and  sides  be  compactly  rammed,  and  the  pressure  on 
the  top  be  evenly  distributed,  as  by  sand  or  gravel.  No 
large  stones  or  lumps  of  clay  should  be  placed  immediately 
on  top  of  this  pipe  in  back-filling. 

Changes  of  direction  in  riveted  pipe  are  made  either  by 
use  of  short  sections  with  converging  or  bevelled  end-planes, 
or  by  means  of  iron  castings.  Branches,  reducers,  and  all 
other  special  constructions  are  made  of  riveted  plates  in  large 
pipes;  and  of  riveted  plates,  but  more  often  of  iron  castings, 
in  small  pipes;  special  designs  being  generally  made  for  each 
case  in  the  riveted  work,  but  the  castings  used  being  stand- 
ard, as  for  cast-iron  pipe. 

The  metal  should  be  tough  and  elastic,  capable  of  shop- 
and  field-riveting  without  any  injury.  The  Rochester  38-inch 
main,  laid  in  1894,  called  for  soft,  open-hearth  steel  con- 
taining not  over  0.6^  of  manganese  and  0.06^  of  phosphorus, 
and  having  a  tensile  strength  of  between  55,000  and  65,000 
lbs.,  an  elastic  limit  of  not  less  than  30,000  lbs.,  and  an 
elongation  of  22\io  in  8  inches.     Cold-bending,  punching,  and 


4l8  WATER-SUPPLY  ENGINEERING. 

similar  tests  also  were  called  for;  and  no  plate  was  to  be  less 
than  95^  of  the  required  thickness  at  any  point.  The  thick- 
nesses varied  between  \  and  f  inch.  Steel  from  o.  i  inch  to 
i^  inches,  or  perhaps  even  thicker,  has  been  used  for  riveted 
pipe.  The  dimensions  of  some  conduits  of  this  pipe  were 
given  in  Table  No.  45,  page  186. 

For  coating  of  riveted  pipe  Angus  Smith's  pitch  was 
found  to  be  unsatisfactory,  and  other  materials  are  being 
tried,  most  of  them  having  asphaltum  as  a  principal  in- 
gredient. The  Rochester,  N.  Y.,  Bundaleer,  Australia,  and 
other  conduits  have  used  a  mixture  of  equal  parts  of  refined 
Trinidad  asphaltum  and  refined  coal-tar.  A  japanning  process 
of  applying  asphalt  is  used  also;  asphalt  dissolved  in  bisul- 
phide of  carbon  ("P.  &  B.")  and  many  other  compounds 
have  been  tried.  The  use  of  riveted  pipe  has  been  too  recent 
to  furnish  a  thorough  test  of  these  coatings.  The  specifica- 
tions for  coating  the  Bundaleer  pipe  (1898-9)  were  as  follows: 

"  30.  Immediately  after  testing,  each  pipe  shall  be 
thoroughly  and  effectually  freed  from  rust  and  dirt  to  the 
satisfaction  of  the  inspecting  officer. 

"31.  The  coating  composition  shall  consist  of  equal  pro- 
portions of  best  Trinidad  natural  asphaltum  and  refined  coal- 
tar,  or  such  modification  of  the  proportions  as  the  Engineer- 
in-Chief  may  consider  advisable.  The  tar  shall  be  kept  for 
about  four  hours  at  a  temperature  of  210°  Fahr.  to  permit 
of  evaporation  before  being  used.  After  these  materials 
have  been  thoroughly  mixed  together  in  a  proper  mixing- 
bath,  they  shall  be  run  into  a  horizontal  dipping-bath  and 
maintained  at  a  temperature  of  not  less  than  350°,  nor  more 
than  400°  Fahr.  during  the  process  of  dipping. 

"As  the  mixture  will  deteriorate  after  a  number  of  pipes 
have  been  dipped,  it  shall  be  cleaned  and  fresh  materials,  in 
correct  proportions,  added  when  ordered  by  the  superintend- 


DESIGNING.  419 

ing  officer.  The  bath  must  be  occasionally  emptied  and 
replenished  with  new  material, 

"32.  No  pipe  shall  be  dipped  until  it  has  passed  the 
hydrostatic  test,  nor  till  it  has  been  approved  by  the  super- 
intending officer  immediately  before  dipping.  Every  pipe 
shall  be  perfectly  clean,  dry,  and  free  throughout  from  rust 
when  the  coating  is  being  applied.  Immediately  before  being 
placed  in  the  bath  each  pipe  shall  be  dried  by  a  blast  of  hot 
air."  It  was  also  provided  that  each  pipe  should  be  dipped 
twice,  remaining  in  the  bath  for  15  minutes  the  first  time, 
and  should  then  be  sprinkled  with  clean  sand ;  the  entire 
coating  of  asphalt  and  sand  to  weigh  "  not  less  than  9  oz. 
per  square  foot  of  both  sides  taken  together." 

Wrought-iron  pipe  weighs  about  10.  i  lbs.  per  lineal  foot 
for  each  foot  of  circumference  and  each  quarter-inch  of  thick- 
ness (the  width  of  laps  being  added  to  the  pipe  circumference 
and  length);  and  steel  about  10.2  lbs.  for  the  same  unit 
dimensions.      Or,  weight  of  steel  pipe 

W=  40.8/(3. 1416./  +  /)(Z  +  /), 

in  which  t  is  the  thickness  of  metal  in  inches,  d  is  the 
diameter  of  pipe  in  feet,  L  is  the  length  of  the  pipe,  and  /  is 
the  lap  at  either  longitudinal  or  circular  joints. 

"  Steel  seems  best  adapted  for  use  (as  compared  with  cast 
iron).  First.  For  the  larger  sizes  of  mains,  say  from  24-inch 
diameter  upwards.  At  about  this  size  the  relative  cost 
begins  to  be  in  favor  of  cast  iron.  Second.  For  what  may 
be  called  leading  mains  in  outlying  districts — force-mains,  and 
similar  work  where  not  likely  to  be  disturbed  or  tapped. 
Third.  As  conduits  in  remote  regions  difficult  of  access,  its 
lightness  and  ease  of  transportation  fitting  it  especially  for 
this  use."  (To  which  may  be  added  mains  subject  to  exces- 
sive pressure.  Thick  cast-iron  shells  are  subject  to  unknown 
cooling-stresses    and    air-holes    and    other    flaws.)     "  Under 


420  WATER-SUPPLY  ENGINEERING. 

these  conditions  the  principle  advantages  in  the  use  of  steel 
are:  First.  Economy  in  first  cost.  This  is  in  many  instances 
the  controlling  factor  in  the  case.  .  .  .  Second.  Less  liability  of 
breakage  while  in  service.  Steel  plate  is  undoubtedly  a  much 
more  reliable  material  than  cast  iron  to  resist  tensile  strains 
and  the  shocks  incident  to  its  use  in  water-mains.  .  .  .  Third. 
Its  adaptability  for  special  situations  when  the  use  of  cast 
iron  would  be  attended  with  risk  or  excessive  cost." 
(L.  M.  Hastings  in  Journal  of  N.  E.  W.  W.  Ass'n,  June 
1899.)  The  flexibility  of  this  pipe  and  use  of  riveted  joints 
seem  to  adapt  it  especially  for  use  in  bridge-crc  sings  and 
other  locations  subject  to  vibration  or  slight  movements 
which  tend  to  open  lead  joints. 

Wrought-iron  pipe  coated  inside  and  out  with  cement  has 
been  used,  but  its  use  has  been  practically  abandoned.  By 
its  use  the  tensile  strength  and  uniformity  of  sheet  metal  is 
obtained,  the  cement  coating  protects  it  from  rust  and  gives 
it  stiffness,  and  does  not  impart  a  taste  to  the  water  as  does 
the  tar  coating  used  on  cast-iron  pipes.  But  cast-iron  pipe 
many  times  as  strong  as  the  wrought  iron  now  costs  15  to 
25  per  cent  less  laid  in  the  line,  is  less  liable  to  damage 
from  handling,  is  more  easily  laid,  and  service  connections 
can  be  made  with  it  more  readily.  In  many  cases  the 
cement-lined  pipe  has  been  entirely  destroyed  by  minute 
cracks  in  the  cement,  which  would  permit  rust  to  form  in  the 
iron  and,  if  on  the  outside,  roots  to  enter  and  peel  off  the 
cement  from  the  outside  of  the  pipe.  However,  if  the 
cement  lining  is  put  en  properly  and  good  materials  used, 
this  pipe  has  some  advantages  over  cast  iron,  particularly 
where  there  is  much  trouble  from  tuberculation. 

Wood  pipe  offers  certain  advantages  over  iron,  particularly 
where  the  cost  of  the  latter  material  or  of  transportation  is 
excessive.  It  is  also  free  from  injury  by  electrolysis.  If  the 
pressure  is  at  all  high,  however,  the  pipe  must  depend  upon 


DESIGXING.  421 

iron  or  steel  bands  for  strength;  and  the  pressure  must  be 
less  than  that  which  will  cause  the  bands  to  crush  the  wood 
fibres.  The  life  of  the  wood,  if  it  be  always  saturated,  should 
be  indefinite,  and  that  of  the  pipe  therefore  depends  upon 
the  bands. 

Small  water-pipe  of  bored  logs  is  now  but  little  used.  It 
is  claimed,  however,  that  1500  miles  of  Wyckoff  water-pipe 
is  in  use,  chiefly  in  the  Middle  and  Western  States.  This 
pipe  is  made  of  wooden  shells,  bored  and  turned  from  solid 
logs  and  banded  spirally  with  iron,  steel,  or  bronze  bands; 
the  outside  being  thoroughly  coated  with  pitch  and  rolled  in 
sawdust.  It  is  claimed  that  this  pipe  can  be  made  to  stand 
150  to  200  lbs.  pressure  with  safety.  For  branches  and  other 
connections  cast-iron  specials  are  used,  the  end  of  the  pipe 
being  driven  tightly  into  the  bell  of  the  casting.  Service 
connections  are  made  with  an  auger  and  a  corporation  cock 
with  lag-screw  threads.  The  cost  is  said  to  be  about  25^  less 
than  that  of  cast  iron. 

Wood-stave  pipe  has  been  used  for  many  years  for  large 
conduits,  such  as  flumes  for  water-wheels  in  New  England 
and  for  hydraulic  mining  in  the  West.  But  during  the  past 
few  years  it  has  come  into  extensive  use  for  water-supply 
conduits.  It  may  be  used  for  pressures  up  to  85  lbs.  when 
made  of  redwood  or  Douglas  fir;  the  limit  depending  upon 
the  ability  of  the  wood  to  resist  crushing.  The  life  of  the 
wood  should  be  considerable,  although  where  exposed  to  the 
air  in  a  dry  climate  evaporation  will  keep  the  outside  nearly 
dry.  The  steel  bands  should  be  coated  with  protective  paint, 
and  if  possible  should  be  repainted  whenever  necessary.  But 
when  the  pipe  is  buried  the  bands  cannot  be  repainted.  To 
enable  them  to  resist  rust  as  long  as  possible  they  should  be 
of  round  rather  than  of  flat  metal;  when  their  life  should  be 
at  least  fifty  years  in  ordinary  soils. 

Experiments  would  seem   to  indicate  that  if  a  wood-stave 


422  WATER-SUPPLY   ENGINEERING. 

pipe  is  exposed  to  a  dry  atmosphere  a  loss  from  percolation 
and  evaporation  of  0.05  gals,  per  day  per  square  foot  of 
surface  may  be  expected;  but  if  it  be  buried,  no  loss  from 
this  cause  is  found  to  occur. 

This  pipe  is  made  of  a  number  of  "staves  of  variable 
length,  having  radial  edges  and  concentric  faces,  and  which 
are  held  together  by  metal  bands  usually  circular  in  section 
and  spread  in  accordance  with  the  demands  of  the  strains 
imposed. 

"  In  the  design  of  a  wood-stave  pipe,  the  following  essen- 
tial points  require  consideration:  The  staves  must  be  thin 
enough  to  secure  complete  saturation  and  to  deflect  readily 
to  the  degree  of  curvature  employed,  and  they  must  be  thick 
enough  to  prevent  undesirable  percolation  through  them. 
The  bands  must  be  of  such  size  that,  when  spaced  to  secure 
the  desired  factor  of  safety  against  rupture,  there  will  at  the 
same  time  be  no  sensible  flexure  in  the  staves  and  no  destruc- 
tive crushing  of  the  fibre  beneath  the  bands.  While  fulfilling 
these  conditions,  the  proportion  between  the  thickness  of  the 
staves  and  the  strength  and  spacing  of  the  bands  must  be 
such  that  the  swelling  of  the  wood  will  not  produce  injurious 
strains  upon  what  might  otherwise  be  a  properly  proportioned 
band.  .  .  .  The  tensile  strains  resisted  by  the  bands  are  from 
three  sources:  (i)  The  initial  strain  caused  by  crushing  during 
construction.  (2)  The  pressure  of  the  water  within  the  pipe. 
(3)  The  swelling  of  the  staves.  The  strains  resisted  by  the 
staves  are  from  the  following  sources:  (i)  The  compressive 
strain  of  the  bands.  (2)  The  compressive  strain  upon  the 
©dges  of  adjoining  staves.  (3)  The  pressure  of  the  water 
producing  flexure  of  the  staves  between  adjacent  bands." 
(A.  L.  Adams,  Trans.  Am.  Soc.  C.  E,,  vol.  XLI.  page  27, 
which  see  for  full  discussion  of  wood-stave  pipe.)  Adams 
considers  Table  No.  71  page  424  to  give  the  most  economic 
proportions  for  staves  and   bands.     The  spacing  of  the  latter 


DESIGNING.  423 

of  course  varies  with  the  pressure.     His  formula  for  this  is  as 
follows : 

/  =  (RJ^it)P-^  E"f      ^^^^"      ^  ^  ^"     ^""^     -^  <  (^  +  0^ 

when     P  >  E"     and     ^  <  (^^  +  f)e 
when     /^  >  E"     and     j  >  (i^  +  Z)^ ; 


in  which /"  is  the  band-spacing  in  inches;  s  is  the  safe  tensile 
strain  in  the  band  in  pounds;  R  is  the  internal  radius  of  the 
pipe  in  inches;  /  is  the  thickness  of  the  stave  in  inches;  P  is 
the  water-pressure  in  pounds  per  square  inch;  ^  is  the  safe 
bearing-power  of  the  wood  in  pounds  per  lineal  inch  of  band 
(about  800  lbs.  per  square  inch  of  contact  surface  of  band  and 
wood);  and  E"  is  the  permanent  swelling  force  of  the  wood  in 
pounds  per  square  inch  (assumed  at    100  lbs.  for  all  spacing). 

The  staves  are  made  to  break  joints  in  the  pipe.  The 
butt-joints  are  made  by  driving  into  kerfs  sawed  in  the  end 
of  each  stave  thin  steel  plates  about  i^^  inches  long  and  some- 
what wider  than  the  stave.  The  bands  are  cinched  by 
fastening  the  two  ends  of  each  band  in  a  cast-iron  shoe,  one 
end  being  provided  with  a  thread  and  nut.  The  bottom  of 
the  shoe  is  made  to  fit  the  outside  of  the  pipe.  Curves  are 
made  in  the  pipe  by  simply  bending  the  staves  during  con- 
struction, which  is  carried  on  in  the  field,  the  pipe  being  built 
in  its  final  position.  Small  branches,  air-escapes,  etc.,  are 
attached  by  fastening  castings  on  the  outside  of  the  pipe  by 
means  of  bands. 

Wood-stave  pipe  should  not  be  coated  on  the  inside,  as 
this  would  prevent  the  saturation  of  the  wood  and  permit 
decay.      No  coating  has  been  found  which  will  remain  on  the 


424 


WATER-SUPPLY  ENGINEERING, 


outside   of  a  pipe  when   it  is  under  pressure;   and   if  buried, 
such  a  coating  would  probably  be  of  no  great  value. 

Table  No.  71. 

ECONOMIC    PROPORTIONS    FOR    PIPE    DESIGNS. 


-« 

c  a» 
1.1 

£■2 

0 

ui  IJ  ,; 

11  § 

15^^ 

5 

c 

e 

(max.value  =  — -, — r-r — -. )" 

\                        rad.  or  band  sec-/ 

^Q 

(55 

H 

« 

fc 

lO 

iiX4in. 

ItV  in- 

15    X    x'ff 

1255 

5-26 

207 

12 

iiX4 

t1 

do. 

1475 

4-47 

207 

14 

1^X4 

'i!*^ 

do. 

1650 

4 

i6 

2X6 

^33 

do. 

1650 

4 

i8 

2X6 

If 

do. 

1650 

4 

20 

2X6 

If 

do. 

1650 

4 

22 

2X6 

If 

# 

1508 

4.4 

122 

24 

2X6 

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1 

1650 

4 

27 

2X6 

T    7 

1 

1650 

4 

30 

2X6 

^5 

\ 

2673 

4-4 

162 

36 

2X6 

lA 

1 

2950 

4 

42 

2X6 

If 

1 
7 

2950 

4 

48 

2X6 

T      1 

i 

2950 

4 

54 

2^X8 

2? 

1 

4600 

4 

60 

3X8 

2i 

1 

4600 

4 

66 

3X8 

2t\ 

3 

6600 

4 

72 

3X8 

2f 

f 

6600 

4 

On  all  pressure  conduits,  blow-offs  should  be  provided  at 
low  points  for  use  in  flushing  all  dirt  out  of  the  pipe.  In 
irrigation  conduits  or  others  which  sand  is  likely  to  enter, 
sand-boxes  and  gates  should  be  provided.  The  sand-box  is 
essentially  an  enlargement  and  depression  in  the  canal,  in 
which  the  reduced  velocity  causes  the  heavier  sediment  to 
settle.  This  sediment  may  conveniently  be  removed  through 
an  opening  in  the  bottom  of  the  sand-box,  or  a  sluice-gate  in 
its  side  at  the  bottom,  through  which,  when  opened,  the 
water  will  wash  out  the  accumulated  deposit. 

At  all  summits  on  closed  conduits  there  should  be  an  air- 
escape.  If  these  summits  are  below  the  hydraulic  gradient 
this  escape  must  be  so  contrived  as  to  permit  air  to  escape, 
but    no   water.     The   ordinary   form    is    shown    in    Fig.    75; 


DESIGNING. 


425 


b  being  a  float  which  remains  up  and  keeps  the  opening  d 
closed  while  the  box  is  full  of  water,  but  falls  and  opens  d  as 
air  rises  into  the  box  and  lowers  the  water.  If  a  fire-hydrant 
or    service  connection   be  placed    at    a   summit,    the   air  can 


Fig.  75. — Air-escape  Valve. 

escape  through  this  and   the  use   of    an  air-escape  valve   is 
unnecessary. 

The  most  desirable  line  from  a  reservoir  or  intake  to  the 
point  of  utilization  is  a  straight  one,  if  the  country  be  level 
and  such  a  location  be  not  expensive  in  right  of  way.  But 
detours  in  a  hilly  country  may  make  as  short  a  line,  or  one 
requiring  less  heavy  pipe,  and  less  lift  if  pumping  be 
employed;  and  such  a  detour  may  be  necessary  to  avoid 
going  above  the  hydraulic  gradient.  It  is  largely  a  question 
of  expense,  and  the  choice  between  routes  should  be  made 
by  comparing  their  cost,  taking  account  of  length  of  conduit, 
thickness  of  pipe  necessary,  accessibility  and  cost  of  right  of 
way,  special  river-crossings,  trestles,  etc.,  required,  and 
increased  pumping  expense  or  size  of  pipe  due  to  lengthened 
line  and  consequent  flattened  gradient.  A  gravity  conduit 
can  be  carried  over  a  summit  above  the  hydraulic  gradient  by 
use  of  a  siphon.  But  this  needs  special  attention  to  remove 
the  accumulated  air  frequently,  and  is  not  advisable  unless 
within  easy  reach  of  the  pumping-station  or  a  maintenance 
force.     The  air  may  be  removed  by  a  small  vacuum-pump;  or 


426  WATER-SUPPLY  ENGINEERING. 

it  may  be  collected  in  an  air-tight  tank  connected  with  the 
summit  of  the  pipe,  the  air  in  the  tank,  as  often  as  it  nearly 
fills  this,  being  replaced  with  water  by  closing  a  valve  at  the 
bottom  of  each  leg  of  the  siphon  and  pouring  water  into  the 
tank. 

In  warm  climates  closed  conduits  may  be  placed  upon  or 
near  the  surface,  although  this  would  render  the  water  too 
warm  for  city  supplies.  But  in  cold  climates  this  would  lead 
to  the  bursting  of  the  pipes  by  freezing;  and  they  must  be 
protected  from  this,  generally  by  burying  in  the  ground. 
Open  conduits  also  in  such  climates  should  have  thick  walls, 
or  earth  banked  against  them,  to  prevent  contraction  of  the 
channel  by  ice  forming  on  the  sides.  Pipes  through  which 
water  is  always  circulating  are  frequently  left  uncovered  where 
crossing  bridges,  without  freezing;  and  as  a  general  rule  it 
may  be  said  that  this  is  permissible  when  the  length  of 
exposed  pipe  in  feet  is  not  greater  than  ten  times  the  square 
of  the  diameter  in  inches,  and  the  velocity  of  flow  is  at  least 
one  fourth  of  a  foot  per  second.  The  danger  that  the  flow 
will  entirely  stop  at  night-time  is  so  great,  however,  that  it 
is  better  to  box  in  such  pipe,  and  fill  the  box  with  mineral- 
wool,  asbestos  or  some  other  non-conductor. 

Water-pipes  in  New  England,  northern  New  York,  and 
the  entire  northern  tier  of  states  should  generally  be  placed 
not  less  than  5  feet  below  the  surface;  below  these,  to  the 
southern  tier,  Af\  to  4  feet  is  the  customary  depth;  and  in 
the  Southern  States  3  or  even  2  feet  is  permitted  for  small 
pipe,  although  when  so  near  the  surface  this  is  in  danger  of 
being  crushed  by  heavy  teams.  A  gravity-closed  conduit,  if 
on  the  surface,  should  be  covered  to  at  least  the  above  depth 
on  top  and  sides.  The  above  measurements  are  to  the  centre 
of  the  pipe. 

A  pipe  conduit  should  rest  upon  a  firm  foundation.  If 
in   rock,    the   bottom  of  the   trench  should   be  covered  with 


DESIGNING.  427 

gravel,  sand,  or  loam  well  rammed  for  the  pipe  to  be  bedded 
on.  The  pipe  should  slope  continuously  to  the  main  depres- 
sions, where  blow-offs  are  provided  discharging  into  a  near-by 
creek  or  sewer  for  removing  any  sediment;  sags  in  the  line 
favoring  accumulations  of  sediment  at  the  low,  and  of  air  at 
the  high,  points.  The  blow-off  may  be  an  ordinary  T,  a  gate- 
valve,  and  a  short  piece  of  pipe  leading  to  the  sewer  or  creek; 
but  it  is  better  to  substitute  for  the  ordinary  T  the  blow-off 
T  shown  in  Fig.  'j'^. 

Curves  of  long  radius  may  be  made  of  chord's  connected 
by  eighth-bends,  or  by  making  a  slight  angle  at  each  joint. 
A  4-inch  pipe  may  be  swung  2  to  2\  feet  out  of  a  straight 
line,  an  18-inch  pipe  10  or  12  inches,  and  a  good  joint  still  be 
made.  But  more  than  this  should  not  be  attempted,  as  the 
lead  joint  cannot  take  a  strong  shape  or  be  well  calked  if 
there  be  too  much  angle. 

In  crossing  streams  the  water-pipe  may  be  laid  in  the  bed 
of  the  stream  or  carried  over  on  a  bridge.  The  former  plan 
is  often  expensive,  and  the  detection  and  repair  of  leaks  is 
difficult.  There  is  also  danger  in  some  cases  that  freshets 
will  carry  away  the  pipe.  On  the  other  hand,  on  an  iron 
bridge  there  are  vibrations  tending  to  cause  leaks,  and  freez- 
ing is  possible;  also  the  bridge  must  have  additional  strength 
to  support  the  pipe  and  its  contained  water.  Over  a  stone 
arch  the  pipe  can  be  laid  underground,  as  in  a  street,  and  the 
only  danger  is  that  of  the  freezing  of  the  pipe  where  the 
covering  both  above  and  below  it  is  thin,  as  it  may  be  over 
the  centre  of  the  arch.  Where  there  is  no  bridge  the  pipe 
must  generally  be  placed  in  the  stream-bed ;  but  where  there 
is  one  it  is  probably  better  to  carry  the  pipe  on  this,  either 
resting  on  the  floor  or  suspended  beneath  it,  and  protected 
from  freezing.  If  the  pipe  rises  to  the  bridge-floor  the  joints 
at  the  elbow  are  apt  to  pull  apart,  and  should  be  tied 
together  by  long  bolts  and  clamp-rings;  or  steel  pipe  ma\' 


428 


WATER-SUPPLY  ENGINEERING. 


be  substituted  for  cast  iron   across  the  bridge  and  for  two  or 
three  feet  beyond  the  elbows  at  each  rising-end. 


Fig.  76. — Bridge-crossings. 

Ordinarily  the  pipe  is  simply  placed  in  the  trench,  the 
joints  made,  and  the  trench  refilled  with  such  tamping  as  is 
required  by  the  nature  of  the  ground  or  street-surface.  But 
where  the  pipe-line  passes  under  a  railroad,  a  building,  or 
other  structure  causing  considerable  pressure  upon  the  soil, 
it  is  desirable  to  protect  the  pipe  from  this,  and  to  protect 
the  structure  from  being  undermined  by  a  break  in  the  pipe. 
In  the  case  of  a  small  pipe  the  latter  may  be  effected  by 
enclosing  this  pipe  in  a  larger  one.  But  a  much  better  plan 
is  to  build  a  heavy  arch  of  brick  or  concrete  over  the  pipe, 
and  fill  the  space  around  the  pipe  with  sand  or  good  earth. 

For  shutting  off  the  flow  at  any  point  in  a  pressure  con- 
duit gate-valves  with  screw-stems  are  used.  Sliding-stem 
valves,  check-valves,  or  any  kind  of  valve,  hinged  or  otherwise, 
by  which  it  is  possible  to  close  the  opening  rapidly  should 
not  be  employed  where  the  pressure  is  more  than  10  lbs. 
Valves  on  underground  pipe  are  reached  through  boxes  which 
surround  the  top  and  stem  of  the  valve  and  extend  to  the 
surface,  where  they  are  closed  by  a  cover.  Valves  on  12-  or 
15-inch  pipe  or  less  generally  stand  with  the  stem  vertical, 
and  the  box  is  either  a  standard  pattern  of  cast  iron,  or  is 
built  around  the  valve  with  brick.  Larger  valves  would 
ordinarily  rise  too  near  the  surface  if  erect,  and  are  laid  upon 
their  sides;  and  the  largest  are  worked  by  gearing.     These 


DESIGNING.  429 

larger  valves  would  require  that  a  manhole  be  built  around 
them,  similar  to  a  sewer-manhole. 

All  rubbing  surfaces  of  valves  should  be  of  bronze,  and 
all  parts  sufificiently  strong  to  resist  the  greatest  pressure 
(including  water-hammer)  which  can  come  upon  either  side. 
Each  valve  should  be  tested  in  place  for  leaks  in  the  stuf^ng- 
box  or  elsewhere. 

The  location  of  valves  and  fire-hydrants  has  already  been 
discussed.  Post  fire-hydrants  are  those  most  commonly  used. 
They  are  generally  placed  upon  the  same  side  of  the  street  as 
is  the  pipe  (this  giving  the  shortest  connecting  pipe  or  branch\ 
and  just  inside  of  the  curb.  The  branch  pipe  may  be  4 
inches  for  2^-inch  nozzles  only,  but  if  a  fire-engine  nozzle  is 
furnished  on  the  hydrant  no  less  than  a  6-inch  pipe  should  be 
used.  For  ordinary  localities  two  hose-nozzles,  with  an 
engine-nozzle  if  desirable,  are  sufficient.  Each  nozzle  may  be 
furnished  with  an  independent  valve,  but  this  is  often  omitted. 
The  main  valve  is  placed  at  the  base  of  the  standpipe  or 
barrel  of  the  hydrant,  and  may  be  either  a  sliding  gate-valve, 
or  a  compression  valve;  and  the  latter  may  close  downward 
against  or  upward  with  the  pressure.  All  these  have  been 
used  with  satisfaction;  and  if  the  material  and  workmanship 
are  good,  a  clear  and  large  water-way  and  easy  curves  at  the 
bends  are  more  important  than  the  style  of  valve.  It  is 
desirable  also  that  it  be  possible  to  remove  the  valve  and 
stem  without  having  to  dig  around  the  hydrant. 

When  the  main  valve  is  closed  after  use,  the  hydrant  will 
be  full  of  water.  If  this  remains  there  in  cold  weather,  it  is 
apt  to  freeze  and  burst  the  hydrant,  and  hence  a  drip  should 
be  provided  which  will  always  be  open  when  the  hydrant  is 
closed,  and  only  then.  Through  this  the  water  escapes  from 
the  hydrant,  and  should  be  led  away  before  it  can  freeze. 
This  is  best  accomplished  by  connecting  to  the  drip  a  i-inch 
pipe  leading  to  a  sewer  or  drain.      If  there  be  no  drain  near 


430 


WATER-SUPPLY  ENGINEERING. 


by,  the  excavation  around  the  hydrant  and  branch  may  be 
filled  with  broken  stone  for  a  height  of  a  foot  or  eighteen 
inches,  which  will  receive  the  water  in  its  interstices  and  from 
which  it  will  gradually  soak  into  the  ground.  If  the  soil  is 
any  but  the  hardest,  the  hydrant  should  be  set  upon  a  large 
flat  stone  to  prevent  it  from   settling  into  the  ground  when 


V  1 


_J 


r>\ 


Fig.  77. — Fike-Hydrant  (Ludlow  Pattern). 

this  becomes  wet  from  the  drip.  A  large  stone  or  small  pier 
of  masonry  should  be  wedged  tightly  between  the  back  of 
the  hydrant  opposite  the  branch  and  the  solid  earth  to 
prevent  the  impulse  of  entering  water  from  forcing  the 
hydrant  off  of  the  branch. 

If  the  branch  leads  from  a  main  10  or  12  inches  or  more 
in  diameter,  it  should  be  provided  with  a  valve-gate  just  out- 
side the  hydrant,  that  any  injury  to  this  may  be  repaired 
without  closing  the  main  pipe.     A   frost-case  is  sometimes 


DESIGNING.  431 

used,  i.e.,  a  cylinder  of  iron  fitting  loosely  around  the 
hydrant-barrel  at  and  for  two  feet  or  more  below  the  ground- 
surface,  to  prevent  the  "frost"  from  "heaving"  the 
hydrant,  which  the  ground-surface  in  this  case  does  not  touch. 
The  use  of  this,  however,  is  being  largely  discontinued  as 
being  unnecessary. 

The  distance  from  the  pavement  to  the  branch  should  be 
at  least  as  great  as  that  to  the  main,  since  this  is  the  more 
liable  to  freeze,  there  being  no  flow  through  it  at  most  times. 

When  placed  at  a  corner  where  a  large  and  small  main 
intersect,  the  hydrant  branch  should  generally  lead  from  the 
larger  pipe.  Fire-hydrants  should  not  be  placed  in  front  of 
buildings  needing  especial  protection  or  which  would  furnish 
a  very  hot  fire,  but  should  be  preferably  about  150  or  200 
feet  from  such  point  on  each  side,  as  in  the  former  position 
they  would  be  inaccessible  in  time  of  fire  on  account  of  heat 
or  falling  walls. 

Probably  ten  times  as  many  fire-hydrants  are  injured  by 
sprinkling-cart  drivers  as  in  any  other  way,  where  these  take 
water  directly  from  the  hydrants.  This  should  not  be 
permitted,  but  "water-cranes" — contrivances  especially 
designed  for  filling  sprinkling-carts — should  be  placed  at  con- 
venient points;  and  all  but  firemen  should  be  prevented, 
under  a  heavy  penalty,  from  opening  a  fire-hydrant.  (At 
Newton.  Mass.,  in  1894,  74  fire-hydrants  out  of  a  total  of 
760  were  damaged  by  employes  of  the  street  and  sewer 
departments.)  A  space  under  each  crane  should  be  paved 
to  catch  the  drip  and  leaking  of  carts,  and  should  be  connected 
with  the  sewer,  or  the  gutter  if  there  be  no  other  drain. 

The  size   of   the  main    conduits  of    an   irrigation   or  city 

supply  system   are  readily  calculated   from  Art.  63  if  the  fall 

in  the  hydraulic  gradient  and  the  maximum  quantity  of  flow 

are  known.*    An  irrigation  main  conduit  should  be  capable  of 

*  See  also  Appendix  D. 


432  WATER-SUPPLY  ENGINEERING. 

passing  in  an  irrigation  season  of,  say,  lOO  days  the  entire 
available  supply;  that  is,  the  yield  minus  reservoir  evapora- 
tion and  seepage.  The  gradient  is  the  grade  of  the  conduit 
itself  if  this  be  open;  if  it  be  closed,  but  if  there  be  an  open 
conduit  or  reservoir  at  each  end  and  the  closed  conduit  be 
uniform  in  bore,  it  is  the  average  fall  from  one  open  end  to 
the  other, 

A  city  conduit  must  carry,  with  the  available  head,  the 
maximum  rate  per  minute  and  still  leave  a  suf^cient  pressure- 
head  at  the  point  of  supply.  The  gradient  will  then  have 
one  end  at  an  elevation  above  the  town  equal  to  the  desired 
pressure-head,  the  other  at  a  distance  below  the  reservoir- 
surface  equal  to  the  entrance  and  velocity-head.  If  the  pipe 
be  continuous  and  of  uniform  bore  the  gradient  will  be  a 
straight  line  connecting  these  points.  If  a  pump  raise  the 
water  to  the  town,  the  further  end  of  the  gradient  will  be  at 
a  distance  vertically  above  the  pump  equal  to  the  pressure- 
head  in  the  main  at  the  pump.      Thus,  in  Fig.  78,  if  A  be 


Fig.  78. — Hydraulic  Gradient  for  Pumping-main. 
the  pressure-head  at  the  town  and  B  that  at  the  pump,  the 
line  CD  will  be  the  hydraulic  gradient,  DE  being  the  friction 
head.  B  can  of  course  be  made  as  great  as  desired,  and  thus 
the  gradient  be  given  any  desired  fall.  A  should  be  at  least 
150  feet  for  cities,  if  possible,  and  100  feet  for  suburban 
districts  and  villages. 

The   maximum   rate   of    consumption    may   be    taken    as 
about  200^  of  the  average  annual  rate,  plus  the  rate  for  fire 


DESIGNING. 


433 


purposes.    This  latter  can  be  taken  from  Table  No.  8,  page  40. 

For  example,  for  a  city  of   10,000  if  the  pressure  and  nozzle 

size   be  such  as   to   discharge   a   fire-stream   of   250  gals,  per 

minute,  3000  gals,  per  minute  will  be  the  maximum  amount 

required   for  this  purpose;   other  consumption  would  have  a 

10,000  X  200 
maximum  of,  say,  — ^ — — =  1400  gals,  per  minute,  or 

a  total  of  4400  gals,  per  minute  as  a  maximum  flow  to  be 
provided  for. 

The  size  of  distributaries  for  irrigation  has  already  been 
considered.  That  of  the  pipes  in  a  city  distribution  system 
is,  however,   more  complex.      If  MA,   Fig.   79,   is  the  main 


c 

B 

T 

V 

N» 

K 

L 

1 

A 
-    D 

G 

1 

E     0* 

F 

«o 

z    .^ 

V 

- 

3       . 

\o 

P 

X 

- 

u  w 

Fig.  79. — Distribution  System. 

conduit,  and  H  a  fire-hydrant  in  service,  the  supply  for  this 
will  come  partly  through  each  of  the  pipes  BI,  AG,  and  DF, 
with  perhaps  some  flow  through  KE.  BK  will  supply  a  large 
part  of  the  discharge  at  N,  and  DE  of  that  at  O,  although  a 
considerable  amount  for  each  will  come  through  AG  and  FI. 
It  might  be  possible  to  so  arrange  and  proportion  the  pipe 
that  the  supply  for  any  fire-hydrant  would  come  equally 
through  all  connecting  lines.  But  this  would  not  be  an 
economical  arrangement,  and  the  plan  generally  adopted  is 
to  design  a  skeleton  system  of  mains  and  fill  in  intermediate 
streets  with  local  distributing  pipes.     This  gives  more  pressure 


434  WATER-SUPPLY  ENGINEERING. 

along  the  main  lines  than  on  the  intermediates,  and  hence 
these  lines  might  be  placed  where  are  the  highest  or  most 
important  buildings,  if  there  be  any  difference  in  this  respect. 
In  general,  the  mains  may  pass  through  every  second  or  third 
street  running  in  one  direction,  and  every  fourth  to  eighth  in 
the  other,  the  remaining  streets  being  filled  with  6-inch  pipe, 
or  perhaps  4inch  in  short  blocks  (a  practice  not  recommended 
by  a  great  many  engineers);  it  being  assumed  that  all  the 
supply  passes  through  the  larger  mains,  which  is  an  error  on 
the  safe  side.  For  instance,  it  is  assumed  that  in  Fig.  79 
AG  carries  the  entire  supply  for  the  line  TU  and  all  below, 
or  \  of  the  entire  supply;  and  that  F^^ carries  from  GS  \  of 
the  supply,  ^toward  [^  and  f  toward  W.  If  the  maximum 
supply  for  the  city  were  4500  gals,  per  minute,  MAG  should 
be  of  such  size  as  to  carry  all  this;  GT,  1500  gals.;  GZ, 
3000  gals. ;  Zi,  2000  gals. ;  lU,  1 000  gals. ;  G^,  3000  gals.; 
4S,  1000  gals.;  4V,  500  gals.;  4.-3,  looo  gals.  ;  j-^,  670 
gals.;  2'W,  330  gals.  Other  considerations  would  change 
certain  of  these  figures,  however.  For  instance,  under  the 
above  arrangement  but  two  fire-streams  are  provided  for  in 
WQ,  whereas  five  or  six  may  be  in  use  at  once  in  these  four 
blocks,  and  the  ability  to  supply  this  number  should  be  made 
the  minimum  limit  for  main  lines,  or,  say,  1500  gals,  per 
minute.  Also  allowance  should  be  made  for  future  exten- 
sions, generally  in  one  pipe  in  each  direction,  as  in  GS  and 
TU. 

A  6-inch  line  should  not  extend  for  more  than  800  to 
1000  feet  between  principal  mains;  nor  a  4-inch  for  more  than 
400  or  500  feet.  If  the  vertical  streets  in  the  figure  are  to 
be  filled  with  6-inch  pipes,  it  is  hence  necessary  to  supply 
more  mains  crossing  the  6-inch  lines,  as  at  TV,  Zj,  and  1-2. 
Each  of  these  may  be  made  of  one  half  the  capacity  of  all 
the  branches  leading  from  it;  for  instance,   TV,  Z3,  etc.,  may 


DESIGNING.  435 


I  -i   V   6' 

have  a  diameter  of  \ =  7-4,  8-inch  being  the  next 

largest  commercial  size.  The  remaining  lines  may  now  be 
made  4-inch,  if  this  size  be  used ;  otherwise  these  also  would 
be  6-inch.  If  the  pipes  are  subject  to  tuberculation,  4-inch 
pipe  should  certainly  be  avoided,  the  effect  of  tuberculation 
upon  this  size  being  so  great. 

In  the  above  the  term  '*  capacity  "  of  pipes  has  been  used 
as  a  convenient  one,  but  *'  capacity  with  a  given  uniform 
friction  head"  is  implied.  If  4500  gals,  per  minute  is  to 
pass  through  JMG,  the  loss  of  head  and  hence  the  pressure 
head  at  G  can  be  found.  If  we  fix  a  minimum  pressure  head 
of,  say,  150  feet  to  exist  at  2  with  six  fire-streams  playing  in 
the  section  WQ,  the  head  at  G  minus  150  will  give  that 
available  for  friction  loss  in  carrying  i  500  gals,  of  water  per 
minute  through  G4.  and  -/— ^.  We  have  fixed  the  capacity  of 
^-j  as  \\  times,  and  G4.  as  \^  times,  that  oi  j-2.  We  may 
assume  a  size  for  j-^,  as  8-inch,  and  ^-j  will  then   (see  Art 


63,    (42))   be   A  /  ■ or  9.26  tnches;    and    G^   will   be 

or    13.9   inches    diameter.      The    head    lost    in 


/ 


n4.5)^ 

passing  1500  gals,  per  minute  through  pipes  of  the  given 
lengths  and  the  above  sizes  is  then  calculated.  If  the  total 
friction  head  thus  found  differs  by  more  than  10^  from  that 
available  (less  than  10^  need  not  be  considered,  as  the  com- 
mercial sizes  of  pipe  will  not  permit  of  small  changes  in  size), 
the  assumed  sizes — 8,  9.26,  and  13.9  inches — may  be  changed 


'  /,  >< 


by  use  of  the  formula    ( -^j  =  f^j    ,   in  which  f  and  d  are 

the  total  lost  head  as  calculated  and  the  assumed  diameter  of 
the  pipe;  f  is  the  available  friction  head,  and  d'  the  diameter 
sought.      No  considerable  refinement  in   these  calculations  is 


43^  IVATER-SUPPLY  ENGINEERING. 

called  for  since  the  commercial  sizes  of  pipe  will  be  used ;  and 
the  assumption  that  all  the  flow  to  2  passes  through  j-2  is 
by  no  means  true,  since  probably  a  fourth  of  it  or  more  comes 
through  Gi2\  also  the  estimate  of  maximum  rate  of  consump- 
tion can  be  made  by  no  means  accurately. 

Where  it  is  supposed  that  an  extension  will  at  some  future 
time  be  made,  a  special  should  be  inserted  for  this  with  a 
plug  leaded  and  calked  in  the  bell  of  the  opening.  At  Q,  for 
instance,  a  cross  should  be  placed,  and  the  right-hand  branch 
plugged. 

Art.  95.     Standpipes  and  Tanks. 

Standpipes  are  made  of  wrought  iron  or  of  steel;  the 
majority  in  recent  years  being  of  the  latter,  although  good 
wrought  iron  is  probably  more  reliable  than  steel  for  this 
purpose.  The  side  plates  are  generally  of  such  width  as  each 
to  build  5  feet  vertical  of  standpipe,  and  are  6  to  9  feet  long. 
The  horizontal  joints  are  generally  single-riveted,  the  vertical 
one  single-,  double-,  or  triple-riveted.  A  few  special  designs 
have  been  employed,  but  generally  a  standpipe  is  circular  in 
plan  and  of  uniform  diameter  throughout,  resting  upon  a 
masonry  foundation.  It  is  sometimes,  but  not  generally, 
roofed  over.  Standpipes  are  much  exposed  to  winds,  and 
hence  should  generally  be  anchered  in  some  way,  or  provided 
with  guys.  When  placed  upon  level  ground  the  lower  30  to 
100  feet  are  in  most  cases  useless  for  either  pressure  or 
storage,  and  this  part  of  the  pipe  is  frequently  replaced  by  a 
tower,  the  whole  thus  becoming  an  elevated  tank  upon  a 
tower. 

The  minimum  height  required  for  pressure  is  calculated 
by  the  methods  already  given.  If  the  country  be  flat,  to 
obtain  a  head  which  would  enable  fire-streams  to  be  thrown 
to  the  desired  elevation  by  gravity  might  require  a  standpipe 


DESIGNING.  437 

200  feet  or  more  high.  Hence  the  domestic  supply  alone  is 
frequently  considered,  and  steam  fire-engines  are  relied  upon 
for  fire-streams;  the  head  being  sufficient  to  bring  to  any 
hydrants  and  connected  steamers  the  desired  quantity. 
There  should  be  contained  in  the  tank,  above  the  elevation 
required  for  pressure,  sufficient  water  to  provide  fire-service 
while  the  boiler-fires  are  being  started  up  and  the  pumps 
enabled  to  supply  the  demand,  even  after  a  night's  consump- 
tion without  pumping.  This  probably  should  be  about  one 
fourth  the  daily  average  consumption  plus  the  water  required 
for  fire-service  during  30  minutes.  This  storage  is  supplied 
by  a  combination  of  height  and  width.  If  the  height  be 
great,  the  pressure  on  the  lower  plates  of  the  tank  is  excessive, 
as  is  that  in  the  distribution-pipes  and  plumbing,  and  the 
pumping  must  be  against  this  great  head.  On  the  other 
hand,  if  the  standpipe  be  made  of  great  diameter  it  increases 
the   cost   both   of   this  and   of  the  foundation. 

Whether  or  no  a  standpipe  shall  continue  to  the  surface 
or  shall  rest  upon  a  tower  is  determined  largely  by  financial 
and  aesthetic  principles.  The  difference  in  cost  of  tower  and 
standpipe  will  not  often  vary  greatly,  but  for  considerable 
heights  or  capacities  the  tower  is  probably  the  cheaper.  A 
standpipe  is  at  best  an  unsightly  object,  although  some 
architectural  beauty  has  been  obtained  by  surrounding  the 
pipe  with  a  masonry  tower  in  a  few  instances,  as  in  Brooklyn, 
N.  Y.  A  more  graceful  structure  can  be  formed  by  a  care- 
fully designed  steel  tower,  an  example  of  which  is  given  in  Fig. 
80a,  the  elevated  tank  of  the  Iowa  State  Agricultural  College, 
designed  by  Prof.  A.  Marston.  As  he  states:  "  The  only 
legitimate  means  for  enhancing  the  architectural  appearance 
of  an  engineering  structure  of  this  kind  are  to  select  pleasing 
proportions  and  graceful  outlines,  and  to  employ  only  neat, 
strong-looking  details.  Any  use  of  sham  ornaments  is 
entirely    out    of    place."      {^Engineering   Nezvs,    vol.    XXXIX. 


438  WATER-SUPPLY  ENGINEERING. 

page  371.)  This  tank  is  24  feet  in  diameter  and  40  feet  high, 
with  hemispherical  bottom,  the  total  height  being  168  feet. 
A  few  tanks  have  been  raised  upon  masonry  towers,  but  this 
construction  is  not  common. 

The  size  of  the  tank  having  been  decided  upon,  and  its 
general  design,  the  thickness  of  plates  can  be  readily  calcu- 
lated. The  stress  in  each  side  of  the  tank  per  vertical  inch, 
due  to  the  contained  water,  can  be  calculated  as  in  the  case 

.434//^ 
of  water-mains ;   the  formula  being  S  = ,  from  which 

T  =  " ,  in  which  5  is  the  tension  in  each  side  per  ver- 

2se  ,  ^ 

tical  inch,  H  is  the  height  of  water  in  feet  above  the  point  in 
question,  f/ is  the  diameter  of  the  pipe  in  inches,  /"is  the  fac- 
tor of  safety,  T  is  the  thickness  of  the  plate  in  inches,  s  is  the 
tensile  strength  of  the  material  per  square  inch,  and  e  is  the 
efficiency  of  the  riveted  joints,  /"is  generally  taken  as  3  to 
5,  probably  the  latter  if  steel  be  employed,  or  2  to  3  if  ^  be 
the  elastic  limit,  c  depends  upon  the  size  and  spacing  of  the 
rivets,  but  is  generally  about  .50  to  .60  for  single,  and  .65  to 
.75  for  double,  riveting.  T  should  never  be  made  less  than  ^ 
inch,  and  seldom  greater  than  i  inch.     The  horizontal  seams 

W 
must  withstand  a  stress  due  to  the  weight  — %  per  lineal  inch, 

TtU 

W^ being  the  total  weight  of  the  tank  above  the  seam;   and  to 

— ~j   per  lineal  inch  due  to  wind-pressure,  P  being  the  pres- 

sure  of  the  wind  per  square  foot,  generally  taken  at  40  to  60 

pounds.     The  total  maximum  stress  on  the  leeward  side  would 

W4-  WP 
therefore  be  ; per  lineal  inch  of  joint. 

Tid         ^  ^ 

The  bottom  plates  of  a  standpipe  rest  upon  the  foundation, 
and  need  to  be  of  only  sufficient  thickness  for  proper  calking 
and  to  allow  for  some  corrosion  on  the  under  side  without 


DESIGNING. 


439 


Fig.  Sou. — Ei.p;vated  Water-tank. 
(State  College  ;  Ames,  Iowa.) 


DESIGNING. 


441 


leaking.  One-half  inch  is  generally  sufficient.  The  bottom 
and  side  may  be  connected  by  flanging  the  edges  of  the 
bottom,  but  a  better  plan  is  to  connect  them  by  a  ring  of 


— ii^i 


< 

C^ 

> 

^  ^Vj  r 

H 

Xh- 

M 

/     V 

0 

/        > 

^^ 

f 

"     / 

50    — 

^Ai 

2" 

angle-iron  on  either  the  outside  or  the  inside,  double-riveted 
to  both  side  and  bottom.  The  top  should  be  furnished  with 
an  angle-iron  stiffener  to  prevent  collapse  by  the  wind,  A 
ladder  should  be  fastened  to  the  outside  of  the  standpipe, 
extending  from  the  top  to  within  about  10  feet  of  the  ground. 


442 


IVA  TER-SUPPL  Y  ENGINEERING. 


The  rings  may  be  truly  cylindrical  and  fit,  every  alternate 
one  inside  the  next  above  and  below;  or  they  may  be  slightly 
conical,  the  upper  edge  of  each  being  outside  the  lower  edge 
of  the  one  above,  to  permit  of  effective  calking  while  the 
standpipe  is  full.  The  contact  surfaces  should  be  perfectly 
clean  when  riveted.  After  riveting  the  pipe  should  be  given 
three  coats  of  paint  inside  and  filled  with  water.  All  leaks 
are  then  calked,  and  when  the  pipe  is  tight  the  outside  should 


NCHOR  BOLT 


Fig.  8i. — Bottom  of  Standpipe. 

be  painted.  The  outside  of  the  bottom  should  be  painted 
before  this  is  lowered  onto  the  foundation. 

An  overflow-pipe  is  occasionally  provided  opening  near 
the  top  of  the  tank,  but  this  is  often  troublesome,  especially 
in  cold  climates.  Neither  it  nor  anything  else  should  be 
placed  inside  a  standpipe  or  tank  in  climates  where  ice  forms. 

The  height  of  water  in  the  tank  can  be  learned  by  a 
pressure-gauge  at  the  pumping-station,  unless  there  is  no 
consumption;  but  consumption  along  the  line  causes  con- 
siderable variation  in  the  pressure  recorded,  and  the  only  safe 
way  is  to  provide  a  telltale  communicating  with  the  pump- 
room  by  wire,  by  which  the  height  of  water  is  indicated  and 
a  bell  is  rung  when  the  water  rises  above  or  falls  below  certain 
elevations. 

The  same  pipe  generally  serves  for  both  inlet  and  outlet 
to  the  standpipe,  and  rises  above  the  bottom  of  this  a  foot  or 
two.     Another  outlet,  flush  with  the  bottom,  may  be  provided 


DESIGNING.  443 

for  washing  out  collected  sediment.  The  inlet-pipe  should 
pass  through  a  tunnel  in  the  foundation  sufficiently  large  to 
permit  of  its  close  inspection  and  repair.  It  should  be 
furnished  with  a  gate-valve  just  outside  the  standpipe,  which 
should  be  under  lock  and  key.  The  junction  of  this  pipe 
with  the  standpipe  is  generally  made  by  riveting  to  the 
bottom  a  flanged  bell-casting,  through  which  the  pipe  is 
passed,  and  in  the  bell  an  ordinary  calked  lead  joint  is  made. 
The  standpipe  should  be  bolted  to  the  foundation,  unless 
its  weight,  W,  in  pounds  exceed  PH^ .  The  bolts  are  gen- 
erally 4  to  8  in  number,  6  or  8  being  preferable.  They  pass 
through  the  foundation,  at  the  bottom  of  which  anchor-plates 
are  used,  and  are  fastened  to  brackets  on  the  side  of  the  pipe 
near  the  bottom.  These  brackets  may  be  made  of  short  pieces 
of  I  beams  and  channels,  riveted  to  the  standpipe;  one  such 
arrangement  being  shown  in  Fig.  8i.  The  maximum  tension 
on    any  anchor-bolt   may  be   found   by  taking  a  wind-pressure 

moment  of minus  the  moment  of  the  weicrht  of  the  tank 

4  "^ 

(considered  empty  for  perfect  safety),  and  placing  this  equal  to 
the  moineiits  of  all  the  bolts  about  the  same  axis  ;  two  calcu- 
lations being  made,  one  witli  the  axis  normal  to  a  radius 
through  a  bolt,  the  other  when  said  radius  bisects  the  angle 
between  two  bolts. 

The  foundation  of  the  standpipe  should  be  made  abso- 
lutely solid,  of  first-class  stone  or  concrete  masonry.  The 
tunnel  admitting  pipes  to  the  standpipe  should  be  substan- 
tially arched  over.  The  top  of  the  foundation  should  be 
perfectly  level.  A  dry  mixture  of  i  part  Portland  cement  to 
I  or  2  of  sand  may  be  spread  about  i^  inches  thick  over  the 
foundation  before  the  bottom  is  lowered  onto  it,  a  ring  of  the 
same  wet  into  mortar  being  placed  just  under  the  edge  of  the 
standpipe.  If  there  is  any  leakage  in  the  standpipe  bottom 
the  cement  will  set   up  and   tend  to  stop  it.      In  any  case 


444  WATER-SUPPLY   ENGINEERING. 

the  sand  offers  a  cushion  for  the  bottom  and  prevents  all  the 
weight  from  coming  on  the  rivet-heads. 

"Tank-steel  "  should  never  be  used  in  standpipes.  "  Shell- 
steel,"  the  next  best  grade,  is  not  advised  for  use.  "  Flange- 
steel  "  is  well  adapted  for  standpipe  use,  being  ductile  and 
uniform  in  quality.  It  costs  above  15  to  20  per  cent  more 
than  tank  steel,  and  4  to  10  per  cent  more  than  shell-steel. 
A  good  standpipe-steel  might  be  specified  as  "  homogeneous 
steel  made  by  the  open-hearth  process,  having  a  tensile 
strength  of  55,000  to  62,000  lbs.  per  square  inch;  an  elastic 
limit  of  not  less  than  32,000  lbs.  per  square  inch;  an  elonga- 
tion in  8  inches  of  20^  in  plates  f  inch  thick  and  under;  of 
22^  for  plates  f  to  |  inch,  and  of  25^  for  plates  |  inch  thick 
and  over,  with  a  reduction  of  area  of  40,  44,  and  50  per  cent 
respectively.  A  cold-bending  test  to  be  made  without  signs 
of  distress  as  follows:  for  plates  up  to  f  inch  thick,  flat  on 
itself;  for  plates  thicker  than  \  inch,  180°  around  a  mandrel 
having  a  diameter  i^  times  the  thickness  of  the  plate.  The 
metal  to  contain  not  more  than  0.04^  phosphorus,  nor  more 
than  0.03^  sulphur."  As  but  a  few  kegs  of  rivets  are  used 
in  a  standpipe,  it  is  noi;  the  general  practice  to  test  the 
material  for  these  at  the  works,  but  to  obtain  the  best  from 
reputable  manufacturers.  A  field  test  of  value  is  to  cut  the 
head  from  a  rivet  which  has  been  headed  in  the  work.  If  the 
head  snaps  off,  the  metal  is  brittle  and  unfit;  but  it  should 
gradually  cut  and  tear  off. 

Elevated  tanks  are  designed  in  the  same  way  as  stand- 
pipes;  except  that  the  bottom  is  often  made  hemispherical 
(as  in  Fig.  80,  page  439)  or  conical;  this  construction  being 
cheaper  than  steel  beams  and  solid  flooring  under  the  tank. 
The  trestle  or  tower  involves  the  ordinary  principles  of 
structural  designing.  Each  post  should  rest  on  and  be 
anchored  to  a  solid  masonry  foundation. 


designing.  445 

Art.  90.     Estimate  of  Cost. 

It  is  generally  desirable,  and  frequently  required  by  law, 
that  a  careful  estimate  be  made  of  the  cost  of  the  work  to  be 
done.  For  this  purpose,  map,  plans,  and  specifications 
should  be  carefully  studied  to  obtain  quantities,  the  character 
of  soil  or  rock  to  be  excavated  should  be  ascertained,  the 
accessibility  of  dams  and  other  parts  of  the  system  con- 
sidered, and  in  general  as  careful  a  study  made  of  the  condi- 
tions as  a  contractor  would  make  before  bidding.  Also  the 
prices  of  materials  and  supplies  should  be  obtained,  including 
the  cost  of  getting  them  upon  the  ground,  and  from  these  as 
dose  an  estimate  made  as  possible  of  the  actual  cost  of 
constructing  the  system.  To  this  should  be  added  lO  to  lOO 
per  cent  for  profit  and  contingencies,  the  latter  amount  when 
the  work  is  to  be  done  under  great  risks  and  subject  to 
possible  losses. 

The  cost  of  CLEARING  AND  GRUBBING  reservoir-sites  may 
-often  be  more  than  met  by  selling  the  timber  for  lumber  or 
fire-wood;  but  aside  from  this  the  cost  of  clearing  ordinary 
timbered  land  will  generally  be  from  $50  to  $500  per  acre.  If 
the  land  is  very  swampy,  covered  with  scrub  second-growth, 
or  if  large  numbers  of  boulders  must  be  removed,  the  cost 
may  be  greater. 

Excavation  of  loam  by  scraper,  including  first  loosening 
it  by  plow,  can  be  done  for  15  cents  per  cubic  yard  if  the 
average  haul  do  not  exceed  looo  feet.  Add  5  cents  per  yard 
for  each  1000  feet  additional  haul.  Stiff  clay  or  light  hardpan 
will  probably  cost  30  to  35  cents  per  yard.  If  the  quantity 
is  less  than  5000  cubic  yards,  or  if  it  must  be  wasted  in  neat 
spoil-banks,  the  cost  will  probably  run  higher. 

Embankment,  i.e.,  spreading  and  compacting  materials 
deposited  from  excavation,  and  facing  the  finished  bank,  can 
be  done  well  for  2  to  4  cents  per  cubic  yard  if  the  necessary 


446  WATER-SUPPLY  ENGINEERING. 

water  can  be  had  close  at  hand ;  otherwise  add  the  cost  of 
obtaining  water.  If  the  embankment  is  less  than  5  feet  high* 
at  either  side,  the  cost  will  probably  be  greater,  and  small 
banks  made  in  dressing  up  reservoir-shores  may  cost  20  or  30 
cents  per  yard. 

Lining  banks  with  broken-stone  and  dry-stone  paving 
1  foot  thick  will  cost  about  4  to  10  cents  per  square  foot 
besides  the  cost  of  the  material.  If  the  stones  are  irregular 
in  shape  and  need  much  dressing  and  fitting,  the  cost  may  be 
increased  two  or  three  times. 

Puddling  will  cost  25  to  40  cents  per  cubic  yard  in 
place,  besides  the  cost  of  the  material  on  the  ground. 

Masonry  for  dam-faces  will  cost  about  $12  to  $18  per 
cubic  yard;  backing  in  Portland  cement  i  :  2,  $5  to  $8  per 
cubic  yard.  This  will  vary  with  the  cost  of  the  stone.  One 
mason  and  helper  should  lay  7  to  10  yards  of  masonrj^  per 
day;  and  each  cubic  yard  of  masonry  will  require  about  \ 
yard  of  sand  and  0.85  barrel  of  cement.  The  cost  of  the  stone 
and  getting  it  to  the  wall,  and  of  mixing  mortar,  must  be 
added.  Dimension  stone  masonry  for  gate-houses,  etc.,  may 
cost  $25  to  $50  per  cubic  yard. 

Timber,  as  in  foundations,  will  probably  cost  $5  to  $15 
per  M.B.M.  more  than  the  cost  of  the  material  on  the 
ground. 

Concrete.  Portland  cement  can  be  had  for  $1.80  per 
barrel  and  up;  natural  cement,  from  65  cents  up.  Sand  at 
all  prices  from  25  cents  per  load  up.  Broken  stone  costs 
about  $1.25  to  $1.75  per  cubic  yard.  Mixing  and  placing, 
if  properly  done,  will  cost  50  to  85  cents  per  cubic  yard. 
For  a  mixture  1:3:5  one  cubic  yard  will  require  \\  barrels 
cement,  0.54  cubic  yard  of  sand,  and  0.9  cubic  yard  of  broken 
stone.  For  thin  layers  of  concrete  on  side  slopes  add  20  to 
60  cents  per  cubic  yard.     Additional  for  timber  forms. 

Flume  Benches  will  probably  cost    12   to    18  cents  per 


DESIGNING. 


447 


cubic  yard  for  excavation  in  loam,  and   50  cents  to  %2   per 
cubic  yard  for  rock. 

Trenches  for  conduits  in  loam  or  loamy  clay,  sand,  or 
gravel  will  cost  about  as  follows.  Sand  and  gravel  must 
generally  be  sheathed.  Hardpan  will  probably  cost  double 
this;   quicksand,  two  to  five  times  as  much. 

COST    OF    EXCAVATING    AND    BACK-FILLING,    AND    OF    SHEATHING 
trenches;    DOLLARS    PER    LINEAL    FOOT. 

(Compact  Loam;  No  Ground-water;  No  Machinery;  No  Street-paving.) 


Depth  of  trench,  feet. 


4-to  lo-inch  pipe 

15-inch  conduit 

20-    "  "  

24-    "  "  

30-    "  "  

Close  sheathing 

Sheathing  planks  4  feet  apart.. 


.055 
.065 

■075 
.085 
.  10 
.  20 
.09 


.065 
.08 
.09 
.105 

.  12 
.21 
.  10 


.075 
.09 

•  ro5 
.  12 
,14 
.22 
.  10 


ID 
125 
15 
175 
20 
.26 
12 


.14 

175 
21 

245 

,28 
32 
.15 


■25 
•315 

38 
.45 

50 
•50 

24 


33 
39 
465 

545 
62 
58 
27 


.32 
.65 
.78 
.91 
1.04 
•75 
•33 


The  cost  of  Closed  Conduits  is  given  in  table  on  page 
448  by  A.  L.  Adams;  the  cast-iron  pipe  being  assumed  as 
costing  $19  per  ton  (the  latest  prices  in  July  1903  are  about 
$30  for  large  pipe  and  $32  for  small;  $19  is  about  the  lowest 
price  ever  reached),  and  steel  plates  at  1.25  to  i.6octs.  (the 
prices  in  July  1903  are  35   to   50  per  cent  higher). 

Cast-iron  Pipe  cost  $29  to  $35  per  short  ton  in  1903; 
special  castings,  2.7  to  3  cents  per  pound.  The  weight  of 
pipe  is  given  in  Table  No.  69,  page  412. 

Laying  cast-iron  pipe  costs  about  as  indicated  in  table  at 
top  of  page  449  (lead  cost  4.55  cents  per  pound  in  August 
1899). 

The  cost  of  Valves,  tested  to  300  lbs.  pressure  is  also 
given  on  page  449. 

These  prices  are  for  iron  bodies  with  bronze  mount- 
ings, and  hub  or  bell  ends.  Flanged  ends  will  cost  5  to  10 
per  cent  more;   all   iron,  about  10  to    15  per  cent  less.      Air- 


448 


WATER-SUPPLY  ENGINEERING. 


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DESIGNING. 


449 


release    valves    for    summits    cost    about  $i8    to    $20    each. 
Valve-boxes  cost  $2.75  to  $3.25  each  for  4-  to  lO-inch  pipe. 

COST    OF    LAYING    CAST-IRON    PIPE  ;    CENTS    PER    LINEAL    FOOT. 


4" 

6" 

8" 

10" 

Unloading,        hauling, 

and  distributing  . 

02  to  0.8 

0.3  to  1.2 

0.4  to  1.7 

0.6  to  2.6 

0.7  to  3.6 

Laying  (labor  at  $1.50). 

0.4  to  0.5 

0.4  to  0.5 

0.5  to  0.7 

0.7  to  o.g 

0.8  to  1.0 

Yarn  (4  to  6  cts.per  lb.) 

0.04  to  0.06 

0.056  to  .084 

.072  to  .108 

.09  to  .134 

.107  to  .161 

Lead  (4  to  5  cts.per  lb.) 

2.06  to  2.58 

2.95  to  3.70 

3.80  to  4.75 

4.80  to  6.00 

5.55  to  7.00 

Coke  and  furnaceman.. 

0.15  to  0.25 

0.15  to  0.25 

0.17  too. 28 

0.19  to  0.31 

0.22  to  0.36 

Yarning  and  calking.  . . 

0.4  to  0.6 

0.5  to  0.7 

0.6  to  0.8 

0.7  to  0.9 

0.8  to  I.o 

Total         

3.25 104.79 

4.356  to  6.434 

5.542  to  8.338 

7.08  to  10.844 

8.177  '0  13.121 

COST    OF    VALVES. 


4" 

6" 

8" 

10" 

6.cx>-7.oo 

9. 80-1 I .25 

i4.7S-'7-oo 

2 I . 00-24 • 00 

22.75-30.50 

14" 

16" 

18" 

20" 

11" 

24" 

30" 

36" 

Cost  (in  dollars) \ 

42.70- 
48.80 

50 . 00- 
57-25 

71-75- 
82.00 

84.75- 
97.00 

109.25- 
125.00 

'31.25- 

150.00 

227.50- 
260.00 

357.00- 
408.00 

Fire-hydrants  cost  about  as   follows  (2  hose-nozzles; 
bronze-mounted;    5  feet  from  ground  to  branch): 


6"Connections. 

4"Connections. 

With  frost-cases 

Without     "           

$22  to  $27 
18  to     24 

$22  to  $25 

iS  to    23 

Add  about  $1.25  for  each  additional  hose-nozzle,  and 
$2.50  for  a  steamer-nozzle;  $2.25  for  each  independent 
nozzle-gate.  For  each  6-inch  increase  or  decrease  in  length 
of  barrel  add  or  deduct  35  to  50  cents.  Fire-hydrants  should 
average  7  to  14  per  mile  of  pipe. 

Water-cranes  cost  about  $25  to  $40  each  for  3-  or 
4-inch  branch-pipe  connections. 

Dug  Wells.    A  well  at  Webster,  Mass.,  25  feet  diameter. 


450 


WATER-SUPPLY  ENGINEERING. 


30  feet  deep,  cost  about  $13,000  (see  Fig.  66,  page  398). 
A  well  in  Addison,  N.  Y,,  \2\  feet  diameter  and  23  feet 
deep,  cost  $2.18  per  cubic  yard  for  excavation  (in  clay  and 
gravel),  cement  masonry  $5.82  per  cubic  yard;  the  total  cost 
being  $637.  The  sheathing,  pumping,  and  special  details 
generally  cost  more  than  actual  excavation  and  lining. 

Tube-wells  at  Savannah,  Ga.,  12-inch  tubing,  cost 
$4.50  per  foot  for  the  first  430  feet,  and  $5  per  foot  below 
that.  In  Pennsylvania,  boring  wells  in  the  oil-regions  cost 
ibout  $1  per  foot;  in  the  Eastern  part,  6-inch  wells  cost  %2 
up  to  200  feet;  from  there  to  500  feet,  $2.75,  and  $3  below 
that.  A  lo-inch  well  on  Long  Island,  290  feet  deep,  cost 
$3.17  per  foot,  in-zluding  tubing.  In  the  Dakotas  wells  in 
1890  cost  about  as  follows: 


Cost  per  Foot. 

SiL,    Inches. 

Average  Depth, 

Feet. 

Average. 

Maximum. 

Minimum. 

8 

912 

$4.16 

6 

840 

5.28 

$6.49 

$2.15 

5 

1087 

4.04 

4i 

654 

4-13 

4.25 

4.00 

4 

794 

3.82 

4.00 

3-50 

3 

440 

1.87 

2.47 

1.50 

2 

308 

.87 

2.61 

0.42 

I 

717 

2.68 

3-25 

0.50 

In  Texas  the  cost  is  from  60  cents  to  $2  per  foot  for 
6-inch  wells  (not  including  tubing),  averaging  about  %\  per 
foot  for  the  first  lOO  feet,  and  35  cents  additional  for  each 
additional  lOO  feet. 

The  average  for  the  fourteen  Western  States  and  Terri- 
tories in  1890  was:   depth,  210  feet;   cost,  Si.  17  per  foot. 

PUMPING-ENGINES  vary  in  price  according  to  the  duty 
required  and,  to  some  extent,  the  head  against  which  they 
work.      Bids   for   2 0,000, 000- gal.    pumps   (including   founda- 


DESIGNING.  45 1 

tions)  in  1895  for  the  city  of  Brooklyn  ranged  from  $62,000 
to  $100,235  each.  A  2,000,000-gal.  compound  pumping- 
engine,  duty  55,000,000,  will  cost  about  $3600;  triple- 
expansion,  duty  80,000,000,  about  $5400.  A  compound 
750,000-gal.  pumping-engine,  duty  30,000,000,  will  cost 
about  $2600;  duty  45,000,000,  about  $3000;  or  duty 
50,000,000,  about  $3200.  These  prices  include  all  piping, 
but  not  the  boilers.  STEAM-BOILERS  cost  about  $1000  for 
a  25-H.P.  to  $20,000  for  a  200-H.P.  water-tube  boiler  of 
high  efficiency, 

A  20-H.P.  Gas-engine  will  cost  about  $1200. 

Two  triplex  power-pumps,  capacity  500,000  gals,  each, 
and  two  25-H.P.  gas-engines  cost  $3500  in  1898. 

Standpipes  cost  about  2^  cents  per  pound  for  erection 
and  painting.  Flange-steel  cost  2.1  cents  per  pound  in 
New  York  in  June  1903.  A  trestle-tower  for  a  standpipe  in 
Jacksonville,  Fla.,  100  feet  high  and  65  feet  diameter  at  the 
base,  cost  about  $8000  in  1898.  The  tank  and  tower  shown 
in  Fig.  80^,  page  439,  cost  $8966,  the  tank  being  24  X  40 
and  the  tower  iio  feet  high. 

A  mechanical-filter  plant  will  cost  approximately 
$10  to  $12  per  1000  gallons  filtered  per  day,  exclusive  of 
building,  foundations,  pumps,  or  piping. 

For  an  ENGLISH  FILTER  no  general  estimate  can  be  made, 
the  cost  depending  largely  upon  the  grading  necessary,  ease 
of  obtaining  sand,  and  other  local  conditions.  From  $20,000 
to  $150,000  per  acre  would  seem  to  be  the  range  of  cost  in 
this  country;  $50,000  being  perhaps  a  fair  average. 

Prices  for  pipe,  pumps,  etc.,  vary  with  the  cost  of  metal. 
Before  making  an  estimate  the  prices  at  that  time  should  be 
learned  from  bids  on  recent  work  or  from  market  quotations 
on  metal. 

Prices  on  excavation,    grading,    etc.,    will   vary    with    the 


452  IVATER-SUPPLY  ENGINEERING. 

material  handled  and  cost  and  efficiency  of  labor.  The  above 
are,  however,  deduced  from  a  large  amount  of  work  in  all 
sections  of  the  country,  and  may  be  used  for  preliminary 
estimates  when  no  local  data  are  available.  Labor  in  all  the 
above  has  been  taken  at  $1.50  and  teams  $3.50  per  day. 
Additional  allowance  should  be  made  for  interest  and 
depreciation  of  plant,  as  well  as  for  contractors'  profit. 


PART  11. 
CONSTRUCTION. 


CHAPTER    XVI. 

SUPERVISION   AND   MEASUREMENT   OF   WORK. 

Art.  97.     Reservoirs. 

After  a  reservoir-site  has  been  cleared,  but  before  any 
excavation  is  begun,  levels  of  the  entire  ground-surface  should 
be  taken  and  a  contour-map  of  the  site  prepared,  with  one- 
foot  intervals  between  contours.  After  the  completion  of  the 
reservoir,  levels  are  again  taken,  referred  to  the  same  bench- 
marks and  base-line,  and  the  amount  of  excavation  and 
embankment  calculated  by  a  comparison  of  these  with  the 
previous  levels. 

Before  excavation,  stakes  for  the  direction  of  the  contrac- 
tor should  be  placed  at  frequent  intervals  along  the  lines  of 
the  inner  and  outer  toes  of  the  embankment,  including  in  this 
the  one  or  two  feet  on  each  side  which  is  later  to  be  removed 
in  shaping  and  dressing  the  slopes.  It  is  desirable  to  place 
monuments  well  beyond  all  danger  of  interference  by  the 
work,  to  which  the  centre  line  of  the  embankment  or  dam  is 
referred ;  they  being  on  each  end  of  an  extension  of  the  centre 
line  if  this  be  straight. 

453 


454  WATER-SUPPLY  ENGINEERING. 

During  the  construction  of  embankments  the  points 
requiring  attention  are:  The  width;  each  layer  must  extend 
the  full  required  distance  beyond  the  finished  face.  Depth 
of  layers;  this  must  at  no  point  be  greater  than  specified. 
Watering;  the  layers  should  be  sprinkled  uniformly  in  all 
parts,  when  wetting  is  required  by  the  character  of  the 
material.  Character  of  material;  each  load  should  be  in- 
spected, and  no  large  stones,  roots  or  other  vegetable 
matter,  or  material  different  from  that  specified,  should  be 
permitted  to  be  dumped.  Form  of  surface;  the  edges  should 
be  kept  higher  than  the  centre.  Rolling;  the  roller  should 
be  of  the  required  weight,  grooved,  and  passed  over  each 
spot  until  it  becomes  solid  and  homogeneous. 

If  a  core-wall  is  used,  this  should  be  kept  a  little  above 
the  embankment,  and  the  latter  should  be  thoroughly  tamped 
where  the  roller  cannot  reach  it. 

Particular  attention  should  be  paid  to  the  puddling  or 
concrete  around  any  pipes  which  pass  through  the  embank- 
ment; and  to  the  total  removal  of  all  top  soil  under  the 
embankment,  and  the  compacting  of  the  first  layer  with  the 
ground  thus  uncovered.  To  insure  the  last,  the  ground 
should  be  plowed  over  after  the  removal  of  the  top  soil. 

After  the  completion  of  the  embankment  templets  are 
set  and  the  slopes  trimmed  by  these.  On  curves,  templets 
should  be  not  more  than  25  to  50  feet  apart,  depending  upon 
the  radius.  On  tangents  they  may  be  50  to  100  feet  apart. 
Each  templet  is  formed  by  driving  a  stout  stake  at  the  foot  of 
the  slope,  and  others  10  or  12  feet  apart  directly  up  the  slope 
from  this.  Care  should  be  taken  that  these  stakes  are  in  a 
plane  normal  to  the  axis  of  the  dam  or  to  a  tangent  to  its 
curve  at  this  point.  To  these  posts  planks  are  nailed  in  such 
a  position  that  the  finished  slope  will  be  a  fixed  distance,  say 
2  feet,  under  their  lower  edges.  The  slope  is  then  carefully 
cut  down  to  the  required  surface. 


SUPERVISION  AND    MEASUREMENT  OF    WORK.        455 

Masonry  work  requires  the  most  careful  inspection,  and 
it  is  frequently  necessary  to  discharge  half  the  masons 
working  before  the  remainder  can  be  compelled  to  obey 
instructions.  It  must  be  remembered  that  the  masonry  must 
be  not  only  strong,  but  also  water-tight.  The  rock  upon 
which  it  is  to  rest  must  be  cleaned  with  brooms  and  then 
washed,  and  should  be  covered  with  a  thick  bed  of  rich 
mortar  just  before  the  masonry  is  started  upon  it.  Every 
stone  used  should  be  perfectly  clean  of  dirt  and  dust.  It 
should  be  lowered  into  its  bed  and  not  rolled  or  barred  into 
place.  Each  bed  should  be  covered  with  an  excess  of  mortar, 
and  no  mortar  should  be  "slushed  "  in  after  the  stone  is  laid. 
It  is  absolutely  essential  that  no  spall  be  driven  under  a  stone 
after  it  is  in  place,  to  level  it  up  or  for  any  other  purpose; 
but  spalls  and  quarry-chips  may  be  used  in  levelling  a  bed 
before  the  stone  is  lowered  onto  it.  In  using  spalls  and 
chips,  however,  these  should  never  be  placed  in  the  bed  and 
mortar  spread  over  them,  but  the  mortar  should  be  spread 
first,  and  the  spalls  forced  into  it.  All  side-  and  end-joints 
as  well  as  beds  should  be  made  in  this  way.  There  should 
be  no  grouting  of  dam  masonry,  for  there  should  be  no  spaces 
for  grout  to  penetrate.  There  should  be  no  dressing  of 
stones  on  the  wall,  but  this  should  be  done  on  the  scaffold, 
or  while  the  stone  is  suspended  from  the  derrick.  Courses 
should  not  be  levelled  up  at  all,  but  should  be  left  as  uneven 
as  possible.  The  above  are  essential  to  a  tigJit  wall,  although 
one  on  which  less  pains  have  been  taken  may  be  sufficiently 
strong. 

The  mortar  should  be  rich — not  more  than  2  of  sand  to  i 
of  cement — and  thoroughly  mixed  before  wetting,  until  it  is 
absolutely  uniform  in  color  throughout.  The  mixing  is  fully 
as  important  as  the  proportions  of  cement  and  sand.  A  slow- 
setting  cement  is  preferable;  and  mortar  should  never  be 
retempered  for  use,  but  on  taking  its  initial  set  in  mortar-box 


456  WATER-SUPPLY  ENGINEERING. 

or  -board  should  be  at  once  thrown  away.  If  the  work  is 
done  by  contract,  it  is  a  good  plan  for  the  party  of  the  first 
part  to  supply  the  cement,  and  thus  remove  the  chief  incen- 
tive for  parsimony  in  its  use. 

Concrete  should  be  thoroughly  mixed,  and  immediately 
put  in  place  and  rammed.  The  broken  stone  should  be  free 
of  all  dust  or  dirt,  and  should  be  wet  before  mixing  with  the 
mortar.  Too  much  water  vvill  ^cause  the  concrete  to  be 
honeycombed  and  porous;  there  should  be  such  an  amount 
that  light  ramming  will  just  bring  moisture  to  the  surface. 
Hard  wood  forms  the  best  material  for  rammers;  and  the 
ramming  should  never  be  heavy,  but  just  suf^cient  to  com- 
pact the  material.  The  faces  of  a  concrete  core-wall  should 
be  plastered  with  i  :  i  cement-mortar  as  soon  as  the  forms 
are  removed  and  before  the  concrete  is  dry;  and  it  is  advisable 
to  give  the  up-stream  face  two  or  three  washes  of  cement- 
and-water  to  increase  its  imperviousness.  All  concrete  should 
be  kept  damp  until  set,  and  should  be  shaded  from  the  sun  if 
possible. 

For  a  distance  of  12  to  20  feet  above  the  ground  a  masonry 
wall  can  be  laid  to  templets,  carefully  set  and  tested  daily. 
Above  this  point  the  faces  of  the  wall  can  be  set  by  offsets 
from  a  transit-line  run  through  its  centre;  or  by  plumbing 
up  from  known  points  in  the  face  below,  the  transit-line  being 
occasionally  used  for  a  check;  the  length  of  offsets  depending, 
of  course,  upon  the  elevation  of  the  point  considered,  with 
reference  to  that  of  the  crest,  which  elevation  must  conse- 
quently be  known.  A  convenient  method  for  obtaining  these 
elevations  on  low  dams  is  to  so  place  a  level  that  its  H.I.  is 
the  elevation  of  the  crest;  the  rod-reading  then  being  always 
the  exact  distance  below  this  of  the  point  on  which  it  is  held. 

Ordinarily  the  test  of  a  dam  or  reservoir  is  filling  it  with 
water.  This  should  be  done  slowly,  particularly  in  the  case 
of  earth  embankments,  slight  porosities  in  which  will  close 


SUPERVISION  AND    MEASUREMENT  OF    WORK.       45/ 

slowly  by  absorption  of  water  unless  the  head  above  them  be 
first  made  so  great  as  to  cause  rapid  percolation  and  leaks. 
Both  masonry  and  earth  dams  may  leak  slightly  for  a  few 
days  or  weeks  after  filling,  but  ultimately  become  perfectly 
tight.  If,  however,  a  leak  begins  to  increase  in  volume,  or 
the  water  is  turbid,  the  reservoir  should  be  at  once  emptied 
and  the  leak  found  and  stopped. 

Earthwork  is  generally  paid  for  by  the  cubic  yard,  and  is 
measured  as  described  above.  Masonry  also  is  paid  for  by 
the  cubic  yard,  there  being  generally  two  classifications  in 
dams,  face-ashlar  and  rubble  backing,  with  a  small  amount 
of  dimension-stone  in  gate-houses  and  ornamental  work. 
The  face-masonry  may  be  paid  for  by  the  square  foot  of 
surface;  or  considered  as  extending  for  a  given  distance  from 
the  face  into  the  wall,  and  paid  for  by  the  cubic  yard.  Gate- 
houses and  similar  structures  may  be  contracted  at  a  lump 
sum  for  all  above  the  foundation;  the  latter  being  paid  for 
by  the  cubic  yard,  since  its  depth  is  not  generally  known 
exactly  beforehand. 

Clearing  and  grubbing  are  generally  done  by  the  acre;  the 
removal  of  top  soil  by  the  square  foot  or  cubic  yard.  The 
handling  of  the  water  of  any  streams  which  flow  across  the 
work  may  be  made  a  lump-sum  item  of  the  contract,  or  may 
be  considered  as  included  in  the  construction  items. 

Lining,  whether  of  concrete,  puddle,  slope-wall,  or  other 
material,  is  generally  paid  for  by  the  square  yard. 

Art.  98.     Conduits  and  Distribution  Systems. 

Before  the  construction  of  a  bench-flume,  slope-stakes 
should  be  set  as  for  a  railroad  cut  (except  that  no  part  of  the 
flume  should  come  upon  the  fill),  and  levels  of  the  surface  be 
taken.  After  grading,  centre  stakes  are  set  and  the  founda- 
tion-piers or  sills  are  constructed,  care  being  taken  to  have 


458  WATER-SUPPLY  ENGINEERING. 

these  the  proper  distance  apart  and  at  the  exact  elevations 
desired.  In  the  construction  of  the  flume  the  character  of 
material,  dimensions,  and  grade  of  the  flume  should  be  made 
to  correspond  to  the  specifications  and  plans. 

The  masonry  in  canal  walls  or  lining  should  be  built  in  the 
manner  specified  above  for  dams.  Canal  embankments  also 
should  be  built  as  are  earth  dams. 

In  the  case  of  stave-pipe  the  staves  should  be  examined 
for  wanes,  shakes,  splits,  knots,  or  other  defects;  and  the 
bands  and  shoes,  for  flaws  of  any  kind.  An  eye  should  be 
kept  upon  the  cinching,  to  see  that  it  is  not  made  too  tight; 
and  upon  the  butt-joints,  to  see  that  each  is  driven  *'  home." 
A  table  should  be  prepared  beforehand  from  the  profile  of  the 
line,  showing  the  proper  spacing  of  bands  at  each  station; 
and  the  stations  should  be  designated  upon  the  ground  by 
stakes  properly  marked. 

In  constructing  riveted  pipe  care  should  be  taken  to. 
prevent  the  abrasion  of  the  coating,  and  if  this  occur,  the 
coating  should  be  renewed  by  use  of  ''  P.  &  B."  paint  or 
other  satisfactory  compound.  Rivet-holes  should  line  up 
within  a  sixteenth  of  an  inch,  and  rivets  be  well  headed  while 
hot. 

Cast-iron  pipe  should  be  inspected  for  blow-holes,  cold- 
shuts,  plugs,  or  other  defects,  and  tested  by  hammer  for 
cracks  while  suspended  over  the  trench.  Each  pipe  should 
be  sent  "  home  "  in  the  bell.  Yarn  should  be  firmly  calked 
into  the  lead-space,  of  such  thickness  as  to  bring  the  bores 
of  the  two  pipes  into  line,  and  leaving  the  required  depth  of 
space  for  the  lead.  The  depth  may  be  ascertained  by  use  of 
a  rule  applied  at  various  points  around  the  inside  of  each  bell. 
The  lead  for  each  joint  should  be  run  in  at  one  pouring,  and 
no  cold-lead  plugs  used.  No  inspector  can  tell  whether  a 
joint  is  being  so  calked  as  not  to  leak;  the  test  must  develop 
this  fact.      It  is  a  good  plan  to  give  all  the  calkers  punches 


SUPERVISION  AND    MEASUREMENT  OF    WORK.        459 

of  different  designs,  and  have  each  mark  plainly  with  his 
punch  each  joint  he  calks.  A  deduction  may  then  be  made 
from  the  wages  of  each  for  all  of  his  joints  which  leak. 

The  trenches  for  buried  conduits  should  be  inspected  to 
see  that  they  are  of  sufificient  depth  and  width,  dug  to  the 
proper  line,  of  uniform  grade  on  the  bottom,  and  that  no  rock 
or  large  stones  protrude  in  the  bottom. 

Bell-holes  for  cast-iron  pipe  should  be  of  such  size  and 
location  as  to  permit  the  barrel  of  the  pipe  to  rest  on  the 
ground;  and  cross-trenches  for  riveters  on  wrought-iron  or 
steel  pipe  should  be  of  ample  size  to  permit  of  good  work. 
In  back-filling,  no  large  stones  should  be  used  before  the 
filling  is  two  feet  high  above  the  pipe;  and  selected  material 
should  be  carefully  tamped  under,  around,  and  on  top  of  all 
pipe,  especially  riveted  and  wood-stave. 

Before  the  excavation  of  trenches  the  centre  lines  of  these 
sliould  be  marked  with  stakes  spaced  lOO  feet  apart  on 
tangents,  but  closer  on  curves;  and  a  stake  should  be  driven 
at  one  side  and  directly  opposite  the  point  where  any  special 
device  or  structure  is  to  be  placed,  and  plainly  marked  to 
indicate  what  this  is — as  A.V.  for  air-valve,  V.  for  valve, 
H.  for  hydrant,  etc. 

The  stakes  for  shallow  canals  and  distributaries  are 
generally  combined  centre  and  grade  stakes.  These  should 
be  tested  for  grade  just  before  the  final  grading  of  the  canal 
bottom. 

In  city  distribution  systems  the  contractor  may  be  given 
a  list  showing  the  distance  of  the  pipe-line  from  the  fence-line 
on  each  street.  But  if  there  be  no  fence,  or  the  location  be 
by  offset  from  the  street  centre,  centre  stakes  for  the  trench 
should  be  set.  These  should  be  a  uniform  distance — say  lOO 
feet — apart,  to  facilitate  finding  them;  and  instead  of  stakes 
large  spikes  may  be  used,  driven  flush  with  the  street-surface. 
A  stake  should  be  driven  where  each  fire-hydrant  is  to  go, 


460 


WATER-SUPPLY  ENGINEERING. 


and  appropriately  marked.  Stakes  should  also  be  driven, 
just  inside  the  curbing,  opposite  the  location  of  each  valve, 
special  casting,  or  other  break  in  the  continuity  of  the 
pipe,  and  marked  V,  T»  +>  etc.  After  the  pipe  is  strung  in 
the  trench,  and  before  calking,  the  inspector  should  see  that 
the  instructions  implied  by  these  stakes  have  been  followed. 

The  contractor  should  be  supplied  with  a  map  of  the 
piping,  showing  not  only  the  size  of  pipe  on  each  street,  but 
also  every  special  piece  which  is  to  be  placed  at  each  point; 
the  latter  information  to  assist  the  teamster  in  delivering 
these  where  they  are  needed.  Fig.  82  shows  a  small  section 
of  such  a  map.     Thus,  at  A  is  required  a  10  X  4-inch  tee,  a 


10X4T 

10  X  6  + 

10  V  1 

A 

8X6  + 
10X8R                                                             6   P 

8  P 

R 

10"    ° 

8" 

10X6T 

10X4T 
10  V 
6  V 

• 

( 

40 

) 

10  X  6  + 

10  P 

0 

T  r~ 

10" 

Fig.  82. — Contractor's  Pipe-and-special  Map. 

lO-inch  valve,  a  10  X  6-inch  cross,  and  a  10  X  8-inch  reducer; 
while  at  i)  an  8  X  6-inch  cross,  a  6-inch  plug,  and  an  8-inch 
plug  are  required. 

The  inspector  should  see  that  the  pipe  is  of  the  required 
weight  (the  weight  of  each  pipe  is  marked  inside  of  one  end 
by  the  manufacturer)  and  without  defect,  and  is  placed  at  the 
correct  location  and  depth ;  that  all  specials  are  placed  where 
directed ;  that  traffic  and  pedestrians  are  not  interfered  with 
more  than  is  necessary;  that  blasting  and  other  operations  are 
so  conducted  as  to  endanger  no  lives;   that  valves  and  fire- 


S[/F£J?J'/SIOJV  AND    MEASUREMENT   OF    WORK.        461 

hydrants  are  in  good  order,  stuffing-boxes  in  shape  for 
service,  drip-connection  (if  any)  carried  to  the  drain  or  sewer, 
hydrants  at  the  right  depth,  vertical,  and  well  supported  and 
braced  as  required.  He  should  also  see  that  the  back-filling 
and  paving  are  done  as  specified. 

The  engineer  should  keep  a  note-book  in  which  is  entered 
each  line  of  pipe,  its  size,  distance  from  the  fence  or  street 
centre,  and  depth  below  the  surface;  with  the  location  of  each 
valve,  hydrant,  or  special  of  any  kind.  The  exact  length  of 
pipe,  hydrant-connections,  etc.,  is  here  recorded;  the  date  of 
beginning  and  completing  the  construction,  and  any  special 
work  calling  for  extra  payment. 

Bench-excavation  is  generally  paid  for  by  the  cubic  yard 
of  earth  and  of  rock.  Conduits  of  whatever  kind  are  paid  for 
by  the  lineal  foot  of  each  size,  band-spacing,  or  thickness  of 
shell;  separate  payments  being  made  for  material  and  con- 
struction, or  one  payment  to  cover  both.  Valves,  hydrants, 
and  other  special  devices  are  paid  for  at  a  price  for  each  in 
position  ready  for  use.  It  is  customary  to  measure  each  line 
of  pipe  from  end  to  end,  making  no  deductions  for  any  inter- 
mediate specials,  these  thus  being  actually  paid  for  twice. 
Where  a  pipe  changes  size  by  a  reducer,  each  size  is  considered 
as  terminating  in  the  middle  of  the  reducer.  Hydrant- 
branches  may  be  measured  as  extending  from  the  centre  of 
the  main  pipe  to  that  of  the  hydrant-barrel. 

The  price  bid  for  laying  pipe  generally  includes  excavat- 
ing, placing  and  calking  the  pipe  and  specials,  and  back-filling 
and  repaving;  but  rock-excavation  is  generally  paid  for  extra, 
by  the  cubic  yard. 

The  price  of  cast-iron  pipe  and  specials  is  usually  stated 
per  ton. 

It  is  extremely  desirable  to  test  all  conduits  and  appurte- 
nances under  water-pressure    before   they  are   covered.     In 


462 


IVA  TEK-SUPPL  Y  ENGINEERING. 


sandy  soil  it  is  almost  impossible  to  discover  leaks  in  an 
underground  pipe;  although  in  clay  or  loam  these  ordinarily 
make  themselves  apparent  at  the  surface  when  at  all  consider- 
able. But  even  in  such  soil  thousands  of  small  leaks  may 
escape  detection  if  the  pipe  be  covered,  and  these  may  and 
do  cause  a  waste  of  5  to  20  per  cent  of  the  consumption  in 
many  systems. 

If  iron  pipe  is  exposed  to  the  sun  for  several  days, 
expanding  by  the  heat  and  contracting  at 
night,  the  joints  are  made  to  leak  by  the 
motion.  It  is  hence  desirable  to  test  each 
section  and  cover  it  the  day  it  is  laid.  If 
the  section  ends  at  a  valve,  the  end  is  closed 
by  this  for  the  test;  but  if  not,  a  tempo- 
rary or  false  head  may  be  fastened  in  the 
end  of  the  last  pipe.  A  convenient  appli- 
ance for  this  is  shown  in  Fig.  83,  used  by 
W.  R.  Hill  on  the  Syracuse  water-works. 
Fig.  83. — False  Head  If  the  pumps  or  reservoir  be  completed 
FOR  Testing  Pipes.    ^^^    ^^^^^    f^^.   service    before  the   conduit 

and  distribution  system  are  laid,  water  for  testing  may  be 
introduced  into  them,  and  the  pressure  contributed,  by  these. 
In  the  majority  of  cases,  however,  the  conduits  and  the 
reservoir  or  pump  are  being  constructed  simultaneously,  and 
this  is  impossible.  The  test  may  then  be  made  by  filling  the 
pipes  by  gravity  or  by  a  small  pump  from  some  stream,  and 
applying  pressure  by  a  small  steam-  or  hand-pump.  The 
water  can  be  introduced  through  a  fire-hydrant  or  a  special 
casting  left  unplugged. 

The  presence  of  air  in  a  pipe-line  during  a  test  may  result 
in  unnecessary  fracture  of  the  pipe.  If  the  advance  end  of 
the  pipe  is  higher  than  the  remainder,  an  opening  must  be 
provided  here  for  permitting  the  air  to  escape;  all  hydrants 
and  air-escapes  must  be  opened;  and  all  air  removed  from  the 


SUPERVISION  AND    MEASUREMENT   OF    WORK.        463 

system  before  the  pressure  is  applied.  If  a  small  hand-pump 
is  used  to  raise  the  pressure,  its  pipe  may  be  connected  with 
a  hydrant-nozzle  by  means  of  a  bushing,  or  it  may  be  con- 
nected with  the  false  head.  While  the  pressure  is  on,  all 
joints  should  be  examined,  and  any  leaks  found  should  be 
calked  until  the  pipe  is  tight  throughout,  when  it  may  be 
covered.  Valves  and  hydrants  as  well  as  pipe  should  be 
tested  under  pressure. 

While  pipe-laying  is  progressing  the  open  end  of  the  pipe 
should  be  closed  with  a  plug  each  night  to  prevent  the 
entrance  of  animals,  or  of  stones,  sticks,  etc.  Some  refuse  is 
almost  sure  to  enter  the  pipes,  however,  and  when  they  are 
first  put  into  service  all  blow-offs  should  be  opened  and  the 
pipes  thoroughly  cleaned. 

Fire-hydrants  should  be  inspected  to  see  that  their  valves 
seat  properly  and  are  tight,  and  that  the  drip  acts  whenever 
the  hydrant  is  closed.  If  the  drip  does  not  act,  the  barrel 
remains  full  of  water,  which  is  apt  to  freeze  in  winter;  if  it 
leaks,  water  is  wasted  and,  if  the  drip  is  not  connected  with 
the  sewer  or  drain,  fills  the  ground  around  the  hydrant, 
preventing  the  latter  from  draining  when  shut  off. 


Art.  99.     Other  Features. 

Pumps  and  boilers  are  generally  set  and  connected  up 
ready  for  service  by  the  manufacturer,  who  is  paid  a  lump 
sum.  In  a  few  instances  it  has  been  provided  that  this  sum 
be  diminished  at  a  fixed  rate  if  the  plant  fall  short  of  a  given 
duty,  or  increased  if  it  exceed  it.  The  testing  of  pumping- 
engines  has  been  discussed  in  Art.  83.  The  quantity  of 
water  pumped  is  measured  either  by  plunger  displacement, 
with  an  allowance  for  slip ;  by  passing  the  discharge  over  a 


464  WATER-SUPPLY  ENGINEERING. 

weir  or  through  a  Venturi  meter;  or  by  discharging  into  a 
reservoir  or  standpipe  of  known  capacity. 

The  foundations  of  the  pumps  and  boilers  are  frequently 
constructed  as  part  of  the  pumping-station.  Plans,  with 
dimensions,  for  these  are  furnished  by  the  manufacturer,  and 
must  be  closely  adhered  to.  If  bolts  are  to  be  built  in  the 
foundation  by  which  to  tie  down  the  engine,  a  templet,  with 
holes  bored  in  the  proper  places  through  which  the  upper 
ends  of  the  bolts  pass,  should  be  used  for  setting  them. 

In  building  the  chimney,  reliance  should  not  be  placed 
upon  a  batter-board,  but  a  bolt  should  be  fastened  in  the 
foundation  at  the  centre  of  the  shaft  and  plumbed  down  to 
after  every  few  feet  of  added  height.  The  foundation  should 
be  perfectly  solid,  carried  down  to  rock  or  hardpan  if  possible, 
and  of  such  size,  unless  on  rock,  as  to  give  a  pressure  of  but 
\\  to  3  tons  per  square  foot.  It  should  be  carried  as  deep  as 
the  pump-pit,  or  as  any  other  excavation  within  50  feet  of  it, 
unless  it  first  reach  bed-rock. 

The  above  requirements  hold  for  standpipe  foundations 
also.  The  standpipe  is  always  erected  by  the  manufacturer, 
and  the  tests  are  those  conducted  at  the  factory  on  the 
material,  and  that  of  filling  the  standpipe  with  water  to 
determine  leakage.  A  standpipe  usually  leaks  when  first 
filled,  but  small  pin-holes  generally  fill  up  in  a  few  days. 
After  the  pipe  is  erected,  but  before  painting,  it  should  be 
carefully  examined  for  riveting  cracks  or  other  flaws.  Defec- 
tive plates  can  be  removed  from  any  part  of  a  completed 
standpipe  and  replaced  with  but  little  trouble. 

Wells  are  driven  sometimes  by  the  city  or  water  company, 
more  often  by  contract  at  a  fixed  price  per  foot.  In  some 
instances  the  contractor  guarantees  a  certain  minimum  yield ; 
in  which  case  the  guarantee  should  extend  through  six 
months  or  more  of  actual  service,  and  should  designate  the 


SUPERVISION  AND    MEASUREMENT  OF   WORK.        465 

depth  to  which  the  ground-water  must  be  lowered  at  the  well 
during  pumping.  In  making  a  test-measurement  the  water 
discharged  should  not  be  permitted  to  flow  upon  the  surface 
near  the  wells,  as  it  may  then  enter  the  ground  and  be 
repumped.  Samples  should  be  taken  every  few  feet  of  the 
material  through  which  the  well  passes.  Care  should  be 
taken  to  have  every  joint  of  the  casing  made  air-tight. 


CHAPTER    XVII. 
PRACTICAL  CONSTRUCTION. 

Art.  100.     Reservoirs. 

Probably  the  easiest  way  to  clear  wooded  land  is  to  dig 
down  to  and  cut  off  all  tree-roots  a  foot  or  more  beneath  the 
surface,  and  then  pull  down  the  trees  by  a  rope  previously 
attached  to  them  some  distance  above  the  ground.  There  is 
then  no  stump  to  remove.  If  there  are  stumps,  these  may 
be  burned  out,  pulled  out  by  a  stump-puller,  or  blown  up  by 
dynamite.  The  trees  being  down,  the  brush  is  next  cut  with 
sharp  brush-hooks  (the  Spanish-American  machete  is  excel- 
lent for  this  purpose).  This  and  the  tree-tops  may  be  burned 
in  piles.  A  contractors'  plow  may  then  be  used  to  loosen 
the  soil  for  afoot  in  depth;  a  heavy-framed,  long-toothed 
harrow  will  drag  out  most  of  the  larger  roots;  and  the  smaller 
roots  and  loam  can  then  be  removed  by  scraper.  This  top 
loam  should  not  be  used  for  embankments,  but  may  be  used 
for  grading  up  low  spots  above  water. 

For  dressing  up  and  banking  the  shores  of  the  reservoir, 
casting  by  shovel  and  short  wheelbarrow  runs  will  generally 
be  found  the  most  effective  methods.  Where  the  soil  is  of 
loam,  sand,  or  gravel,  or  any  material  easily  loosened  by 
plow,  the  scraper  is  probably  the  most  economical  method  of 
excavating  and  embanking;  unless  the  haul  exceed  about 
looo  feet,  when  a  cart  filled  by  hand  is  more  economical. 

466 


PRACTICAL    COXSTRUCTION.  4^7 

In  either  case  the  ground  should  be  well  loosened  by  means 
of  a  rooter-plow  and  a  2-  to  6-horse  team.  A  wheel-scraper 
is  preferable  to  a  drag  for  most  work.  In  making  embank- 
ment several  scrapers  should  be  used,  and  should  travel  a 
regular  route,  coming  on  the  embankment  generally  at  one 
or  both  ends,  and  leaving  it  at  the  other  end  or  the  middle. 
One  scraper  to  each  300  or  400  feet  of  distance  travelled  by 
them  will  generally  keep  all  hands  busy;  there  being  one  man 
in  the  hole  loading  scrapers,  one  on  the  bank  to  dump  them, 
and  a  driver  accompanying  each  team. 

If  carts  be  used,  two  are  generally  provided  for  each 
team,  one  being  loaded  while  the  other  is  being  hauled  to  the 
embankment  and  dumped;  the  number  of  men  loading  each 
cart  being  just  sufficient  to  fill  it  while  the  team  is  absent 
with  the  other.  This  number  will  of  course  depend  upon  the 
length  of  haul  and  ease  of  shovelling.  If  the  haul  is  of 
considerable  length,  it  will  be  better  to  use  three  carts  to  two 
teams,  or  even  four  to  three  teams.  Under  some  conditions, 
where  time  is  a  very  important  consideration,  teams  may  be 
distributed  at  a  uniform  distance  of  75  to  150  feet  apart  over 
the  whole  course  and  pass  continuously  around  the  circuit, 
being  loaded  by  receiving  a  shovelful  from  each  of  50  to  75 
men  as  they  pass  them,  and  stopping  only  to  be  dumped. 
But  this  is  not  generally  an  economical  method. 

It  pa}-3  to  keep  in  good  shape  the  road  by  which  carts  or 
scrapers  travel  from  the  pit  to  the  dump.  On  a  clay  or 
sandy  soil,  which  is  heavy  in  wet  or  dry  weather  respectively, 
a  good  road  can  be  made  of  plank  spiked  to  two  1 2-foot 
stringers  and  made  up  in  sections  8  feet  long,  with  about 
2  feet  of  each  stringer  protruding  beyond  each  end  of  the 
section;  alternate  sections  having  their  stringers  at  the  ends 
of  the  road-plank  and  about  one  foot  from  the  ends.  This 
forms  a  portable  road  which  will  give  a  good  surface  if  laid 
on  levelled-off  ground.     The  width  may  be  6  or  8  feet;  and 


468 


WATER-SUPPLY  ENGINEERING, 


1 8   or  22   feet  B.M.  per  running  foot   is  required   for  these 
widths  (see  Fig.  84). 

Wetting  of  the  embankment  should  be  done  by  a  spraying- 
nozzle  on  a  hose  or  watering-cart.  Puddles  are  formed  if  a 
bucket  be  used.  In  case  a  stream  is  flowing  near  by  above 
the  elevation  of  the  embankment  this  can  be  brought  for  use 
by  constructing  a  temporary  earth,  timber,  or  brush  dam 
across  it  and  from  this  carrying  a  flume  to  a  point  above  the 


'■       i'         I        '.      T 


NN^M'i/H^YfY^lTrlT^ 


Fig.  84. — Portable  Plank  Road. 
embankment.  Here  a  gate  can  permit  of  filling  a  sprinkling- 
cart,  or  a  hose  can  be  attached ;  the  surplus  water  discharging 
from  the  flume  below  the  embankment.  This  method  can 
often  be  employed  on  storage-reservoirs.  If  the  flume  would 
be  too  long,  however,  or  the  temporary  dam  too  expensive, 
it  may  be  cheaper  to  fill  the  sprinkling-cart  directly  from  the 
stream  by  means  of  a  boat-pump,  diaphragm-  or  other  hand- 
pump,  and  cart  it  to  the  embankment.  In  constructing  a 
distributing-reservoir,  carting  water  is  generally  necessary. 

For  dressing  the  face  of  an  embankment  a  broad  grub-axe 
is  the  best  tool.  A  foothold  is  furnished  by  a  plank  having 
cleats  nailed  to  it  about  a  foot  apart,  which  is  kept  from 
sliding  down  the  bank  by  a  stake  driven  at  its  lower  end. 
The  bank  is  first  graded  under  the  templet,  beginning  at  the 
top,  and  is  surfaced  by  eye  between  templets.  Selection 
should  be  made  by  trial  of  men  who  can  obtain  the  most 
uniform  surface  in  this  manner.  The  surplus  dirt  can  be  used 
for  filling  in  low  places  left  for  this  purpose. 

Puddle  material,  when  made  by  mixing  different  materials, 


PRACTICAL    CONSTRUCTION.  •  469 

should  be  measured  and  turned  over  carefully  by  hand,  with 
as  much  thoroughness  as  is  concrete,  before  being  put  in 
place.  It  may  then  be  thoroughly  rolled;  but  a  better 
puddle  is  made  if  it  be  rammed  by  barefooted  or  rubber- 
booted  men  with  small-headed  rammers,  or  if  trodden  by 
cattle.  In  India,  goats  are  much  used  for  this  purpose,  and 
they  were  used  on  the  Santa  F6  Dam  in  this  country.  If 
there  be  lumps  of  clay  in  the  material,  these  should  be  fine- 
cut  by  spades  before  mixing;  but  if  ready-mixed  hardpan  be 
used,  this  may  first  be  rolled  to  break  up  the  lumps,  and  then 
wetted  and  puddled.  Puddle  should  never  be  wet,  but  only 
damp,  and  the  materials  should  be  thoroughly  mixed. 

Broken  stone  for  lining  must  generally  be  carried  to  the 
top  of  the  slope  and  from  there  lowered  to  where  wanted, 
wooden  chutes  being  convenient  for  this  purpose.  Slope- 
wall  stone  is  delivered  to  the  workmen  in  the  same  way. 
Concrete  for  slopes  is  frequently  delivered  through  chutes; 
but  when  it  is,  it  should  be  remixed  before  using,  as  the 
stone  is  sure  to  separate  out.  It  is  better  to  construct  a 
wheelbarrow  run  along  the  slope,  maintaining  it  at  such  a 
position,  by  frequently  moving  it  up  the  slope,  that  the 
material  can  be  dumped  directly  upon  the  top  of  concrete 
already  in  place.  It  should  never  be  dumped  upon  the 
ground,  to  slide  or  roll  down  the  slope.  If  a  plank  be  held 
as  shown  in  Fig.  85  to  catch  the  concrete  when  dumped, 
none  need  be  wasted.  The  run  can  rest  upon  supports  driven 
in  the  bank  as  shown,  and  spaced  about  6  feet  apart. 

Concrete  on  slopes  should  be  laid  in  horizontal  and  not 
vertical  strips;  as  by  the  latter  method  that  at  the  bottom, 
not  being  set  before  the  top  is  placed,  will  be  pushed  out  of 
position  by  the  weight  of  that  above,  and  the  whole  strip  of 
concrete  tend  to  slide  down  the  bank.  Concrete  lining  should 
be  lightly  rammed,  and  carefully  brought  to  surface. 

Concrete  for  the  bottom  should  be  dumped  where  needed, 


470  '  WATER-SUPPLY  ENGINEERING. 

and  never  shovelled  up  off  the  ground.  Both  here  and  on 
the  slopes  the  proper  thickness  and  surface  elevation  can  be 
obtained  by  the  use  of  horizontal  strips  on  edge,  the  top  edge 
being  at  the  elevation  of  the  concrete  surface,  to  serve  as 
guides  (see  Fig.  85,  a). 


Fig.  85. — Concreting  Slopes. 

Where  the  slopes  are  to  be  paved,  masons'  scaffolds  can 
be  constructed  as  in  Fig.  85. 

If  a  masonry  dam  be  less  than  20  feet  high,  probably  the 
best  way  of  handling  the  stone  is  by  derricks  on  the  ground. 
If  it  be  higher  than  this,  derricks  can  be  placed  upon  the 
dam,  and  provided  with  main-falls  sufficiently  long  to  reach 
the  ground  and  raise  the  materials  from  there.  But  the 
derricks  must  be  raised  continually  as  the  dam  rises;  and  this 
raising  is  a  source  of  expense,  and  of  delay  unless  done  out 
of  working-hours.  To  permit  of  raising,  the  guys  should  be 
adjustable  in  length.  A  gin-pole  can  be  used  for  lifting  the 
derrick-masts. 

In  some  instances  a  travelling  derrick  is  used,  the  track 
being  supported  on  a  scaffold  which  rests  against  one  face  of 
the  dam.  The  cableway  has  been  much  used  of  late  for 
bringing  material  to  the  dam,  and  is  generally  the  most 
economical  contrivance  when  the  dam  is  of  considerable  size. 
A  cableway  667  feet  span  between  towers,  used  for  construct- 
ing   the  Sodom    Dam,    cost    $3750    erected    ready   for    use. 


PRACTICAL    CONSTRUCTION,  47 1 

Spans  of  1500  feet  and  more  have  been  used.  The  cable  is 
generally  used  for  bringing  the  material  from  the  cars  or  carts 
at  one  end  of  the  dam  to  where  it  is  needed,  but  not  for 
setting  the  stones,  both  because  the  cable  extends  only  over 
the  centre  line  of  the  dam,  and  because  its  swaying  prevents 
a  nice  adjustment  of  the  stone.  Hand-derricks  are  generally 
used  for  setting  the  stone. 

Water  for  mixing  mortar  and  washing  the  stones  can  be 
brought  by  flume,  as  for  embankments,  or  in  casks  by  derrick 
or  cableway. 

In  the  construction  of  storage-reservoirs,  the  handling  of 
the  stream  is  frequently  troublesome  and  difificult.  It  is 
generally  necessary  to  carry  it  over  the  heart- wall  trench  in  a 
flume.  The  outlet-pipes  and  base  of  the  gate-house  may  be 
constructed  first,  and  the  stream  turned  through  these,  it  being 
meantime  carried  around  the  structure  in  its  natural  channel, 
or  in  an  artificial  canal  or  flume,  into  which  it  is  turned  by  a 
temporary  diverting  dam.  The  great  danger  is  from  sudden 
floods;  and  until  such  time  as  the  dam  forms  a  basin  capable 
of  holding  so  much  of  the  entire  maximum  yield  of  a  storm — 
say  3  to  5  inches  over  the  entire  drainage  area — as  the  outlet- 
pipes  will  not  discharge,  this  dam  and  flume  should  be  able 
to  carry  such  flood  around  the  works.  Should  water  overflow 
an  embankment  it  may  destroy  it.  If  a  masonry  dam  under 
construction  is  overflowed,  it  may  afterward  be  necessary  to 
remove  the  top  stones  because  of  cement  washed  out  of  and 
dirt  deposited  in  the  joints.  Derricks  and  all  movable  plant 
are  likely  to  be  washed  away,  also.  It  is  of  course  desirable 
to  build  the  lower  part  of  a  dam  during  a  season  free  from 
rain-storms;  and  this  is  particularly  true  of  a  cut-off  wall,  or 
such  part  of  the  dam  as  is  below  the  natural  surface. 


472  wa  ter-suppl  y  engineering. 

Art.  101.     Distribution  System. 

Iron  pipe  is  generally  delivered  to  a  contractor  in  gondola 
cars  on  a  siding,  and  must  be  unloaded  and  distributed  by 
him.  Ordinary  4-,  6-,  and  even  8-inch  pipe  can  be  loaded 
onto  a  wagon  by  rolling  it  down  two  skids  about  9  feet  apart 
placed  from  the  wagon  to  the  top  of  the  car-side;  it  being 
controlled  by  a  rope  passing  around  each  end,  one  end  of 
which  is  fastened  to  the  car  and  the  other  held  by  hand 
and  payed  out.  Two  men  in  the  car  lift  the  pipe  onto  the 
skids  and  hold  the  ropes,  and  one  in  the  wagon  receives  it. 
For  heavier  pipe  three  or  four  men  in  the  car  and  two  in  the 
wagon  are  required;  or  a  yard-derrick  or  portable  stiff-leg 
may  be  used  for  unloading. 

The  pipes  are  distributed  along  one  side  of  the  street, 
and  care  should  be  taken  that  they  are  the  right  size  and 
that  just  sufficient  are  strung  along  each  block  to  lay  the  line 
without  any  rehandling.  In  unloading,  one  end  of  the  pipe 
is  placed  on  the  ground  while  the  other  rests  in  the  wagon, 
a  bag  of  hay  is  placed  under  the  tail  of  the  wagon,  upon  which 
the  pipe  falls  when  the  wagon  is  started  forward.  Pipes  are 
generally  delivered  on  the  side  of  the  street  opposite  that  on 
which  they  are  to  be  laid. 

In  excavating  trenches  the  paving  is  generally  placed  on 
the  side  toward  the  centre  of  the  street,  the  dirt  toward  the 
sidewalk.  By  this  arrangement  the  pipes  do  not  need  to  be 
lifted  over  the  dirt-pile  when  placed  in  the  trench.  Fig.  86 
shows  a  method  of  preventing  the  excavated  dirt  from  block- 
ing the  sidewalk  and  from  stopping  the  gutter-flow.  The 
first  earth  cast  out  should  be  thrown  to  what  will  be  the 
outside  edge  of  the  bank,  since  it  cannot  be  thrown  there 
when  the  trench  is  deeper  without  double  handling. 

Excavating  in  winter  is  expensive,  but  must  sometimes  be 
done.      It  is  facilitated  by  thawing  the  surface  along  the  line 


PR  A  CTICA  L    CONS  TR  UCTION. 


473 


of  the  trench.  This  has  been  done  by  the  application  of 
manure  for  a  day  or  two  before  excavation,  or  of  salt.  But 
a  cheaper  and  better  method  is  that  used  in  Providence,  R.  I. 
Two  boxes,  72  feet  long,  24  inches  wide,  and  12  inches  high, 
are  placed  close  together  in  parallel  lines  on  the  line  of  tlie 
proposed  trench,  all  joints  and  the  ends  being  covered  with 
bagging  and  earth.     These  are  then  filled  with  steam  from  a 


Fig.  86. — Excavation-platform. 

portable  boiler  through  a  f-inch  steam-hose.  The  cost  of 
thawing  by  this  method  was  1.7  cents  per  square  foot. 

In  blasting  rock,  the  drill-holes  should  be  3  or  4  inches 
deeper  than  the  required  trench-bottom;  with  certain  kinds 
of  rock  or  pitch  of  strata  still  deeper  holes  may  be  necessary. 
Each  blast  should  be  covered  by  bundles  of  branches  or  small 
trees  tied  into  fascines,  or  by  planks  or  logs  chained  together; 
the  former  better  preventing  small  stones  from  flying.  If  the 
earth  banks  near  by  are  not  quite  solid,  they  should  be  braced 
before  the  blasting.  In  case  of  boulders  it  is  often  cheaper 
to  remove  these  bodily  than  to  blast  them  in  the  trench  at 
risk  of  caving  the  banks. 

It  is  desirable  to  place  the  pipe  in  the  trench  as  soon  as 
possible.  If  caving  of  the  banks  then  occurs,  only  the  bells 
need  to  be  uncovered  for  making  the  joints. 

Four-,  six-,  and  eight-inch  pipe  can  be  lowered  into  the 
trench  by  two  men,  by  means  of  ropes  passed  around  either 
end  of  the  pipe.     Each  man  slips  under  one  end  of  the  pipe, 


474  WATER-SUPPLY  ENGINEERING. 

as  it  rests  on  the  bank  of  the  trench,  a  knotted  end  of  a  rope. 
Standing  on  this  he  holds  the  other  end  in  his  hand,  and,  by 
paying  it  out,  lowers  the  pipe  into  the  trench.  Then, 
straddling  the  bank,  these  men  lift  the  pipe  clear  of  the 
trench-bottom,  while  a  third  pushes  it  home  into  the  bell  of 
the  pipe  last  laid,  a  fourth  meantime  passing  a  strand  of 
packing  around  the  spigot  of  the  pipe  just  back  of  the  bead, 
and  guiding  it  into  the  bell.  The  third  man  is  provided  with 
a  wooden  bar  which  he  thrusts  into  the  bell-end  a  foot  or  so, 
and  by  which  he  pushes  and  lifts  the  pipe.  With  this,  under 
the  foreman's  direction,  he  lifts  the  pipe  into  the  correct 
position.  A  straight  line  of  pipe  takes  less  piping  to  cover  a 
given  distance  than  does  a  crooked,  the  joints  are  more  easily 
made  and  stronger,  and  it  has  a  more  workmanlike  appear- 
ance. 

For  heavy  pipe  some  other  method  of  lowering  is  neces- 
sary, and  some  form  of  derrick  is  generally  used ;  one  light 
and  easily  portable  being  necessary.  Fig.  87  (from  Ejig. 
NezvSy  vol.  XXXV)  shows  a  good  appliance  for  this  work,  for 
heavy  pipe.  The  derrick  is  carried  along  the  trench  by  three 
men,  and  is  rolled  from  street  to  street  on  its  own  wheels. 
For  light  pipe  the  drum  and  wheels  may  be  omitted,  the  fall 
being  payed  out  by  hand.  While  being  lowered,  the  pipe  is 
guided  by  the  two  men  in  the  trench.  Before  lowering,  the 
pipe  is  rolled  onto  skids  which  span  the  trench,  and  which  are 
removed  when  the  pipe  is  suspended  from  the  derrick. 

The  laying  of  pipe  should  be  begun  at  a  special  whose 
position  is  fixed — as  a  valve,  or  an  intersecting  pipe-line. 
The  pipes  are  laid  in  succession  until  near  where  another 
special  comes,  when  this  special  is  put  in  place  and  the 
closing  length  of  pipe — which  will  generally  be  less  than  a 
full  length — is  temporarily  omitted,  the  laying  beginning 
again  with  this  special.  Behind  this  gang  come  two  men 
who  fit  and  cut  the  closure.     The  length  required  is  accurately 


PRA  CTICA  L    CONS  TR  UCTION. 


475 


measured,  and  a  piece  about  \  inch  shorter  is  cut  from  a  pipe, 
and  is  sprung  into  place  by  raising  one  or  two  pipes  on  either 
side  of  it,  entering  spigots  into  bells,  and  dropping  all  into 
position  again.  In  cutting  cast-iron  pipe  a  ring  is  marked 
around  the  pipe  for  a  guide,  a4X4  to  6x6  pillow-block  is 
placed  under  the  pipe  at  this  ring,  and  by  successive  applica- 

^'^5  'Iron 
jfjlA-' do.- ■ 


End  .Elevation . 


Side    Elevation. 


Fig.  87. — Pipe-derrick. 


tions  of  a  dog-chisel  (Fig.  88,  i)  and  8-  or  lO-pound  sledge  a 
slight  cut  is  made  around  the  pipe.  This  cut  is  made  deeper 
and  deeper,  the  pipe  being  meantime  rolled  back  and  forth 
along  the  pillow-block,  and  the  blows  of  the  sledge  being 
made  heavier  and  heavier,  until  at  length  the  pipe  breaks  off 
at  this  ring.  If  the  iron  be  good  and  the  sledge-blows  not 
too  heavy  at  the  beginning,  there  is  little  danger  of  breaking 


476  •  WATER-SUPPLY  ENGINEERING. 

the  pipe  except  where  desired.  Iron  chips  are  apt  to  fly  into 
the  eyes  of  the  workmen  during  this  operation,  and  eye-shields 
of  transparent  celluloid  are  recommended  for  use. 

Fire-hydrants  are  set  and  their  branches  laid,  generally 
by  this  second  gang,  and  the  blocking  placed  behind  the 
hydrant.  All  valves  and  specials  and  other  appurtenances 
requiring  lead  joints  are  set  in  position,  in  order  that  the 
lead-gang  may  not  need  to  revisit  this  line. 

After  the  pipe  is  laid  a  '*  yarner"  places  the  packing.  A 
tightly  twisted  length  of  packing,  long  enough  to  go  around 
the  pipe,  is  inserted  between  the  bottom  of  a  bell  and  its 
spigot,  and  pushed  back  to  the  shoulder  of  the  bell;  the 
spigot  being  lifted,  if  necessary,  by  driving  a  steel  wedge 
between  it  and  the  bell,  until  the  annular  space  at  the  bottom 
is  slightly  greater  than  that  at  the  top.  The  packing  is  then 
calked  tightly  back  against  the  shoulder  of  the  bell  all 
around,  more  being  added  where  necessary  to  leave  just  the 
required  depth  of  lead  space.  Tarred  packing  can  be  calked 
harder  and  is  easier  to  handle  than  untarred.  To  hold  the 
molten  lead  in  the  joint  when  it  is  poured,  either  a  "  roll  " 
or  a  jointer  are  required.  The  former  is  made  of  well- 
tempered  fire-clay  and  a  strand  of  rope  a  little  longer  than 
the  circumference  of  the  pipe.  The  rope  is  embedded  in  a 
roll  of  the  clay,  and  this  is  rolled  back  and  forth  on  a  smooth, 
wet  board  until  a  roll  of  about  an  inch  in  diameter  is  formed 
with  the  rope  for  its  core.  This  is  placed  around  the  pipe 
against  the  face  of  the  bell,  the  rope-ends  on  top,  and  pressed 
firmly  against  both  spigot  and  bell-face,  the  two  ends  being 
brought  together  on  top  a  little  distance  from  the  bell,  so 
that  a  pouring-hole  is  formed  between  the  bell  and  the  roll 
about  i^  inches  across  each  way.  Into  this  hole  the  lead  is 
poured  slowly  but  steadily  until  it  is  about  to  overflow  the 
pouring-hole.  In  lo  or  15  seconds  the  lead  will  be  hard,  and 
the  roll  may  be  removed  and  smoothed  up  for  the  next  joint. 


PRACTICAL    CONSTRUCTION.  47 7 

The  weight  of  the  lead  frequently  forces  off  the  roll,  particu- 
larly on  large  pipes,  and  the  lead  runs  out.  For  this  reason 
and  because  of  their  general  convenience  patent  jointers, 
made  of  canvas,  asbestos,  and  other  substances,  are  to  be 
preferred. 

The  lead  is  melted  in  a  kettle  supported  in  a  small 
portable  furnace,  in  which  charcoal  is  ordinarily  used  for  fuel. 
The  furnace  is  generally  simply  a  sheet-iron  cylinder  with 
grate  and  coal-door  at  the  bottom,  and  two  dogs  at  the  top 
for  supporting  the  lead-kettle;  but  furnaces  can  be  purchased 
mounted  on  wheels  and  with  short  stove-pipes  attached  to 
the  closed  top.  The  molten  lead  is  carried  from  the  kettle 
to  the  pipe  in  a  ladle,  from  which  it  is  poured  into  the  joint. 
If  the  pipe  be  larger  than  lo  or  12  inches,  a  two-handled 
ladle  is  necessary,  handled  by  two  men  both  on  the  surface 
and  in  the  trench ;  and  for  very  large  pipe  the  lead  is  poured 
from  a  kettle  suspended  over  the  joint  by  a  light  derrick. 

When  the  roll  or  jointer  is  removed,  the  lip  of  lead  at  the 
pouring-hole  is  cut  off,  a  chisel  is  driven  lightly  between 
lead  and  pipe  all  around,  and  the  calking  tools  are  then  used 
(see  Fig.  88).  The  lead  at  the  bottom  is  compacted  first, 
and  calking  proceeds  up  both  sides  until  the  top  is  reached. 
In  calking  pipe  up  to  16  or  18  inches  in  diameter,  the  calker 
passes  one  arm  around  each  side  of  the  pipe,  holding  the 
calking-tool  in  one  hand  and  the  hammer  in  the  other.  For 
calking  very  large  pipe  the  men  work  in  pairs;  each  hooking 
a  leg  and  arm  in  that  of  his  fellow,  one  holds  a  calking-tool 
and  the  other  the  hammer  in  his  free  hand,  and  they  are  thus 
able  to  reach  the  bottom  of  the  pipe.  The  lead  should  be 
upset  and  thoroughly  driven  until  there  is  no  more  "  give  " 
to  it.  The  lips  and  other  pieces  of  lead  are  saved  and 
remelted. 

The  line  is  now  ready  to  be  tested ;  and  after  all  leaks  are 
stopped    by    recalking,    the    trench    may    be    refilled.       The 


478 


WATER-SUPPLY  ENGINEERING. 


author's  remarks  in  "Sewerage"  (pages  212  and  268)  on 
back-filling  and  repaying  are  applicable  to  water-pipe  trenches 
also  and  will  not  be  repeated. 

In  placing  the  ordinary  extension  valve-boxes,  their  tops 
should  be  set  a  little  below  the  top  of  the  filling,  and  two  or 


Fig.  88. — Yarning  and  Calking  Tools  and  Hammer. 
I.    fipe'cutting    Chisel.      2.   Yarning-iron.      3.   Calking-tool.      4.   Calking- 

hammer. 

three  times  as  much  above  the  original  street-surface;  when 
the  trench  has  settled  they  will  then  be  flush  with  the  surface, 
as  they  should  be. 

Every  end  supposed  to  be  plugged  should  be  inspected 
just  before  it  is  buried,  to  make  sure  that  the  plug  is  there 
and  leaded  in  and  calked. 

In  crossing  streams  under  water  the  methods  described  in 
"  Sewerage,"  Art.  79,  may  be  employed.  Many  other  plans 
have  been  followed  however,  the  details  varying  in  almost 
every  case.  At  Delray,  Mich.,  a  72-inch  pipe  was  put 
together  in  two  sections,  each  about  95  feet  long,  bulkheads 
were  built  in  each  end  of  these,  they  were  floated  over  a 
trench  dug  in  the  bottom  to  receive  them,  and  sunk  to  place 
by  admitting  water  into  them,  the  abutting  ends  being 
connected  by  a  diver.      In  another  case  a  main  1 19  feet  long. 


PRACTICAL    CONSl^RUCTION.     ■  4/9 

weighing  63,300  lbs.,  48  inches  diameter,  was  lowered  as  a 
whole  by  derricks.  In  other  cases  pipes  have  been  lowered 
singly  and  jointed  by  divers.  But  in  the  majority  of  cases 
flexible  joints  are  used,  on  every  pipe  or  at  intervals  of  several 
pipes.  The  pipe  is  then  laid  from  scows,  through  the  ice,  or 
connected  on  shore  and  dragged  across  the  river-bottom. 
Several  methods  are  described  in  the  Transactions  of  the 
American  Society  of  Civil  Engineers,  vol.  XXXIII.  pages  264, 
273,  281,  284,  and  vol.  XXXIV.  page  31.  A  12-inch  flexible- 
joint  pipe  laid  across  Hell  Gate,  East  River,  N.  Y.,  cost  $7 
per  lineal  foot  in  place. 

Art.  102.     Wells. 

Dug  wells  for  water- works  are  generally  not  less  than  12 
feet  in  diameter,  and  should  always  be  sheathed  and  braced. 
They  are  generally  circular  in  plan,  since  a  given  amount  of 
material  will  thus  make  a  stronger  wall  and  give  greater 
capacity.  The  sheathing,  however,  is  seldom  made  circular, 
owing  to  the  difficulty  of  forming  the  wales  or  ribs. 
(Sheathing  is  not  required  when  the  walls  of  the  well  are  built 
above  the  surface  and  sunk  bodily  into  the  ground.)  It  is 
generally  made  square  or  octagonal  in  plan,  each  course  of 
wales  being  composed  of  four  or  eight  lengths  of  4  X  4  to  12 
X  12  timber,  strongly  braced  together  at  the  ends;  as  at  a 
and  b,  Fig.  89.  It  is  not  advisable  to  make  any  one  wale- 
piece  more  than  8  or  10  feet  long,  and  6  feet  is  a  safer  limit 
unless  braces  are  used  across  the  well.  This  limits  an 
unbraced  well  to  12  to  20  feet  outside,  or  say  9  to  iG  feet 
inside,  diameter.  Braces  across  a  well  which  is  larger  than 
this  require  to  be  stiffened  against  buckling,  and  the  danger 
of  collapse  increases  rapidly  with  the  diameter.  For  large 
wells  the  method  d  may  be  adopted,  the  excavation  being 
practically  an  annular  trench  around  the  earth  core  rt',  which 


48o 


WA  TER-SUPPL  V  ENGINEERING. 


can  be  well  braced,  and  will  not  collapse  because  of  the  failure 
of  one  brace  or  wale.  This  trench  is  carried  to  the  required 
depth  and  the  wall  is  built  in  it,  earth  being  packed  between 
the  wall  and  the  outer  sheathing  as  the  former  is  built,  and 
all  braces  being  left  in.  After  the  wall  is  completed  the 
centre  core  is  excavated  and  inside  sheathing  removed.      The 


Fig.  89. — Sheathing  Dug  Wells. 

braces  may  be  sawed  off  at  the  inside  face  of  the  wall;  or 
may  be  pulled  out  and  the  openings  in  the  brickwork  filled 
up,  or  these  may  be  left  to  serve  as  weep-holes.  This  con- 
struction can  be  used  for  any  size,  shape,  and  depth  of  well. 

With  either  of  these  methods  the  earth  is  best  removed 
by  "  staging"  it  out,  down  to  about  15  feet,  below  which  a 
derrick  and  large  dirt-buckets  are  more  economical.  The 
derrick  may  be  placed  on  d  in  the  annular-trench  plan,  but  is 
preferably  placed  a  few  feet  back  from  the  well  on  firm  soil. 
If  the  well  be  large,  two  or  three  derricks  will  be  necessary. 
The  booms  should  be  long  enough  to  remove  the  dirt  some 
distance  from  the  well;  unless  it  be  immediately  carted  away, 


PRACTICAL    CONSTRUCTION.  48 1 

which  is  the  better  plan,  since  the  weight  of  extra  dirt  on  the 
surface  around  the  well  adds  to  the  strain  on  the  wales  and 
braces,  and  none  should  be  placed  within  20  or  30  feet  of  the 
excavation.  At  30  feet  depth  a  horse-power  derrick  can 
handle  three  half-yard  buckets  filled  by  six  men;  below  this 
not  so  many  diggers  per  derrick  can  be  used.  With  a  steam- 
power  derrick  four  one-yard  buckets  and  15  to  18  men  can  be 
kept  busy.      These  quantities  are  approximate  averages. 

Another  method  of  sinking  wells,  which  does  away  with 
bracing,  consists  of  sinking  the  masonry  lining  into  the 
ground  by  its  own  weight.  A  stiff  timber  or  iron  footing  is 
placed  in  the  bottom  of  an  ordinary  hand-dug  well  8  or  10 
feet  deep,  and  on  this  the  masonry  wall  is  built.  When  the 
wall  has  been  carried  to  the  ground-level,  the  soil  is  excavated 
from  under  the  footing  equally  all  around,  and  the  wall  sinks 
of  its  own  weight.  This  operation  is  continued,  the  wall 
being  kept  built  up  to  the  surface-level,  until  the  required 
depth  is  reached.  The  footing  is  generally  a  foot  or  two 
larger  than  the  wall,  and  is  frequently  provided  with  a  sharp 
cutting-shoe  around  its  outer  edge.  The  outside  of  the  wall 
should  be  plastered  and  made  smooth,  or  board  sheathing 
placed  around  it  nailed  to  furring  built  in  the  wall,  to  reduce 
the  friction  between  the  wall  and  the  soil  if  the  latter  caves, 
as  it  generally  does.  The  greatest  danger  is  that  the  well 
will  get  out  of  plumb  by  the  more  rapid  settling  of  one  side 
than  of  the  other.  If  the  wall  "hangs"  at  any  time  and 
refuses  to  settle  vertically,  the  excavation  under  the  footing 
should  be  stopped  at  a  uniform  level  all  around  and  not  more 
than  6  to  12  inches  under  the  footing,  and  not  continued 
until  the  wall  has  settled  down  to  a  bearing.  Care  must  be 
taken  that  the  excavation  under  the  footing  is  at  all  times 
level.  A  "  hung"  wall  is  lowered  by  building  it  higher  or 
loading  it  on  top  with  pig  iron,  helped  in  extreme  cases  by 


482  PVA  TER-SUPPL  y   EXGINEERING. 

the  careful  application  of  water-jets  around  the  outside  of  the 
well  to  loosen  the  soil. 

In  all  well-work  the  water  must  of  course  be  kept  out. 
For  this  purpose  a  pulsometer  is  excellent  for  handling  small 
amounts  of  water,  a  centrifugal  pump  for  larger  amounts. 
Reciprocating  pumps  are  frequently  used,  but  are  subject  to 
great  wear  from  muddy  water;  they  have  the  advantage  of 
compactness,  however.  A  centrifugal  pump  is  generally  run 
by  belt  from  the  surface.  If  electricity  is  available,  an 
electric  motor  geared  to  the  centrifugal  pump  is  advisable, 
since  the  belts  are  apt  to  slip  in  a  damp  well,  and  are  greatly 
in  the  way. 

Pump-pits  are  built  in  the  same  manner  as  are  wells, 
except  that  their  walls  are  made  heavier  and  water-tight  and 
a  water-tight  foundation  is  provided. 

Small  i^-  or  2-inch  wells  not  more  than  30  or  40  feet  deep 
are  sunk  through  the  softer  soils  by  simply  driving  them 
down  with  a  hammer;  but  this  is  generally  impracticable 
through  hardpan  and  large  gravel,  and  of  course  through 
rock.  Such  small,  shallow  wells  are  not  advised  for  water- 
works, but  2\  to  lo-inch  wells  through  clay  or  rock  should 
generally  be  employed.  The  best  method  of  sinking  these 
in  most  cases  is  by  the  "  jetting  down  '*  process.  A  small 
pipe,  whose  diameter  is  about  one  third  to  one  half  that  of 
the  well-casing,  is  placed  inside  the  casing  and  water  is  forced 
through  it  by  a  pump,  passing  up  between  the  two  pipes  and 
out  at  the  top  of  the  larger.  The  jet  from  the  bottom  of  the 
water-pipe  loosens  the  soil,  and  it  is  carried  up  by  the 
ascending  water.  As  the  soil  is  thus  removed  the  casing  is 
driven  down  by  a  hammer.  The  water-pipe  is  generally 
given  a  churning  up-and-down  motion  in  firm  soils.  In  sand 
or  loam  it  will  in  most  cases  drop  more  rapidly  than  the 
casing  can  be  made  to  follow.  An  arrangement  for  this  work 
is  shown   in   Fig.   90.      As  both  water-  and  casing-pipe  are 


FKA  CTICA  L    CONS  TR  UCTIOJV. 


483 


lowered  they  are  extended  by  screwing  additional  pieces  onto 
their  top  ends.  The  casing  is  held  upright,  and  the  water- 
pipe  is  supported  and  churned,  by  a  derrick.  Ropes  from  the 
water-pipe  and  hammer  pass  through  sheaves  at  the  top  of 


Fig.  90. — Apparatus  for  Jetting  Down  Wells. 

the  derrick  to  a  two-drum  hoisting-engine,  or  a  cam-and-lever 
well-boring  engine.  In  sand  and  clay  10  to  20  feet  per  hour 
can  be  sunk  by  this  method.  The  most  difificult  material  is 
gravel,  the  jet-water  passing  out  through  the  gravel  and  not 
up  the  casing. 

Rock  of  course  cannot  be  bored  by  this  method,  but  when 
this  is  encountered  either  a  diamond-drill  is  used,  or,  as  is 
more  common,  a  two-,  three-,  or  four-sided  cutting-drill,  to 
which  are  fastened  drill-rods  and  "  jars  "  to  increase  the  force 
of  the  blow,  the  drill  being  raised,  revolved  and  let  fall  with 


484  WATER-SUPPLY  ENGINEERING. 

each  blow.  The  drill  is  lowered  through  the  casing.  If  the 
casing  is  to  follow  through  the  rock,  an  expansion-drill  is  used. 
The  chips  are  washed  out  of  the  hole  by  water-jet. 

A  casing  can  generally  be  driven  400  to  800  feet,  after 
which  the  friction  becomes  so  great  as  to  prevent  further 
motion.  A  smaller  casing  is  then  lowered  inside  this  and 
carried  down  another  400  to  800  feet. 

The  casing  is  generally  lap-welded  wrought-iron  pipe,  with 
screw-joints;  the  coupling  being  made  by  a  sleeve;  by  a 
*'  flush-joint,"  i.e.,  half  the  thickness  of  the  metal  is  removed 
from  the  outside  of  one  pipe  and  the  inside  of  the  other  for  a 
distance  of  3  to  6  inches  from  the  end,  and  threads  are  cut 
on  these,  the  pipes  when  screwed  together  being  thus  flush 
both  inside  and  out;  or  by  an  "  inserted  "  joint — one  end  of 
each  pipe  being  expanded  and  threaded  inside,  thus  prac- 
tically forming  a  sleeve. 


PART  III. 

MAINTENANCE. 


CHAPTER    XVIII. 
RESERVOIRS,   HEAD-WORKS,   AND   INTAKES. 

Art.  103.     Maintaining  Quality  of  Water. 

The  necessity  for  maintaining  a  watershed  free  from  all 
sewage  or  excreta  has  been  explained.  The  most  desirable 
means  of  effecting  this  is  to  purchase  such  watershed  entire; 
but  this  is  seldom  feasible.  As  much  of  a  margin  around  the 
reservoir  as  possible  should  be  obtained,  however;  and  such 
laws  as  exist  or  can  be  got  through  the  legislature  for 
preventing  the  pollution  of  reservoir-sites  and  watersheds 
should  be  strictly  enforced. 

Vegetation  should  be  cleared  from  the  borders  of  a  reser- 
voir at  least  twice  a  year,  and  nothing  but  lawn  and  evergreen 
trees  and  shrubs  should  be  allowed  within  50  feet  of  the 
shores.  No  loafing,  picknicking,  or  bathing  around  or  in  the 
reservoir  should  be  permitted;  but  driving  or  walking  around 
it  on  roads  or  paths  it  is  well  to  encourage.  It  is  desirable 
to  construct  a  gutter  a  little  distance  back  from  the  shore  which 
win  catch  all  surface-flow  and  lead  it  into  the  reservoir 
without  washing  the  roads  or  paths. 

485 


486  WA  l^ER-SUPPL  V  ENGINEERING. 

No  cattle  should  be  allowed  to  enter  the  streams  feeding 
the  reservoir.  If  the  land  through  which  these  pass  cannot 
be  purchased,  arrangements  can  sometimes  be  made  with  the 
farmers — such  as  constructing  new  cow-stables  for  them  for 
pasturing  their  cattle  elsewhere,  and  cultivating  the  banks  of 
the  creeks. 

Swamps  are  not  desirable  on  a  watershed,  and  should  be 
drained  or  filled  in;  and  no  stagnant  pools  should  be  per- 
mitted anywhere.  It  is  seldom  that  a  farmer  will  object  to 
replacing  a  surface-privy  with  a  water-tight  cesspool,  if  it  be 
at  the  expense  of  the  city  or  water  company;  and  this  should 
be  done,  and  the  cesspool  examined  at  least  once  a  year  to 
insure  its  being  properly  cleaned.  The  contents  of  cesspools 
should  be  removed  from  the  watershed.  In  every  way  the 
good  will  of  the  farmer  should  be  kept;  and  the  consumers 
should  also  be  encouraged  to  make  their  influence  felt  with 
such  of  them  as  they  may  come  in  contact  with  in  a  business 
way,  to  the  end  that  the  watershed  be  kept  free  from 
pollution. 

If  vegetable  matter  left  on  the  reservoir-site  or  carried  in 
by  the  run-off  causes  algs  or  other  pollution,  every  efTort 
should  be  made  to  prevent  the  water  distributed  from  suffer- 
ing thereby.  Only  the  purest  water  in  the  reservoir  should 
be  taken  into  the  conduit;  before  the  fall  turn-over  the  foul 
bottom- water  should  be  drawn  off;  and  at  least  once  a  year 
advantage  should  be  taken  of  low  water  to  clean  the  upper 
slopes  of  the  reservoir-bottom,  care  being  taken  not  to  pollute 
the  water.  Grass  and  weeds  should  not  simply  be  mowed, 
but  the  cuttings  should  be  removed  and  not  permitted  to  fall 
or  blow  into  the  reservoir. 

In  short,  all  organic  matter  should  be  removed  and  kept 
out  of  the  reservoir  at  all  times.  This  does  not  apply  to  fish, 
which  are  beneficial  to  a  reservoir,  and  a  number  of  clean 
lake-fish  should  be  supplied  if  not  already  present.    The  fish- 


J^ESEKVOIJiS,  HEAD-WORKS,  AND    INTAKES,  4S7 

screens  should  be  kept  clean  at  all  times.  An  excellent 
scraper  for  cleaning  screens  of  sheet  brass  is  the  rubbei 
"  squegee  "  used  for  cleaning  large  windows. 

If  organic  matter  is  found  to  have  collected  in  a  reservoir, 
it  should  be  removed  and  the  bottom  and  sides  of  the 
reservoir  thoroughly  cleaned.  The  beginning  of  the  rainy 
season  is  the  best  time  for  cleaning  a  reservoir,  A  storage- 
reservoir  should  not,  of  course,  be  emptied  except  when  the 
distributing-reservoir  contains  sufficient  water  to  last  for 
several  days,  including  fire-service.  If  there  be  no  distnbut- 
ing-reservoir,  small  pools  of  water  may  be  made  at  the 
mouths  of  the  feeding-creeks  by  temporary  earth  dams,  and 
the  reservoir  then  emptied  and  cleaned ;  the  water  from 
these  pools  being  led  to  the  conduit  by  wooden  flumes  laid 
on  the  reservoir-bottom,  and  the  supply  thus  maintained. 

When  distributing-reservoirs  are  to  be  cleaned,  the  water 
from  the  storage-reservoirs  or  pumps  is  generally  carried 
direct  to  the  city  through  a  by-pass  around  the  reservoir. 
The  cheapest  method  of  cleaning  a  small  reservoir  with  paved 
bottom  and  sides  is,  generally,  to  flush  out  the  sediment  with 
water.  In  the  case  of  a  distributing-reservoir  a  hose  can 
often  be  used,  the  water  being  obtained  under  pressure  from 
the  pumps  or  the  storage-reservoir.  The  waste-  or  mud-pipe 
being  open,  cleaning  is  started  at  the  end  furthest  from  the 
outlet  and  at  the  highest  point  needing  it;  and  is  continued 
around  the  upper  edge  of  the  sediment,  which  is  washed  and 
scraped  toward  the  outlet  by  hose  and  scrapers  similar  to 
snow-shovels,  the  whole  of  the  material  being  worked  from 
all  sides  toward  the  waste-pipe;  the  surplus  water  meantime 
flowing  out  through  this  and  carrying  away  the  lighter 
matters.  The  algae  and  some  other  deposits  are  gelatinous 
until  dry,  when  they  form  a  leathery  layer  dif^cult  to  remove 
in  this  way.  For  this  reason  the  sediment  should  be  kept 
wet;    generally    by    closing    the    waste-pipe    at    night,    thus 


488  WATER-SUPPLY  ENGINEERING. 

flooding  the  reservoir-bottom  until  work  is  resumed  in  the 
morning.  It  is  often  desirable  to  empty  a  reservoir  slowly, 
cleaning  the  bottom  as  the  water  lowers,  and  thus  giving  the 
sediment  no  opportunity  to  dry. 

In  large  reservoirs  or  those  with  unprotected  earth  bottoms 
or  having  no  mud-pipe  this  method  is  inapplicable,  and  the 
deposit  must  generally  be  removed  by  either  wheelbarrows  or 
carts.  It  is  desirable  to  complete  the  cleaning  without  loss 
of  time,  but  the  material  should  be  as  dry  as  possible,  and  to 
effect  this  the  reservoir  should  be  emptied  quickly.  For  this 
reason,  also,  dry,  hot  weather  is  to  be  preferred;  but  it  is 
generally  inadvisable  to  empty  the  reservoir  at  a  time  when 
it  cannot  be  quickly  refilled. 

Whether  wheelbarrows  or  teams  are  used  for  removing 
the  deposit  will  depend  upon  the  same  conditions  as  in  the 
case  of  reservoir-construction. 

Water  for  irrigation  should  be  kept  free  from  sand  and 
gravel,  which  is  also  necessary  to  prevent  rapid  destruction 
of  the  conduits;  but  few,  if  any,  other  matters  which  are 
ordinarily  received  by  stored  waters  are  objectionable.  Sand 
is  excluded  by  properly  arranged  head-gates,  but  must  be 
kept  cleared  away  from  these  by  use  of  the  flushing-out 
sluices  (Fig.  64,  page  388).  Experience  will  soon  show  how 
often  these  must  be  used  in  any  given  plant;  in  some  cases 
after  every  storm,  in  others  only  once  or  twice  a  year,  while 
in  a  few  cases  it  may  be  desirable  to  leave  the  sluices  open 
during  every  flood  to  prevent  an  accumulation  of  sand  which 
might,  during  one  storm,  exceed  the  intercepting  capacity  of 
the  gates. 

Art.  104.     Maintaining  Quantity  of  Water. 

The  reservoir  should  be  kept  as  tight  as  possible.  Any 
leaks  which  develop  should  be  repaired;  and  if  the  dam  be 
of  earth,  it  should  be  emptied  immediately  if  the  leak  appears 


I^ESEMVOIJ^S,  HEAD-WORKS,  AND    INTAKES.  489 

to  be  increasing  or  if  the  water  from  it  is  at  all  muddy,  as  a 
rupture  is  then  imminent.  If  the  water  run  perfectly  clear, 
however,  and  do  not  increase  in  quantity,  such  desperate 
measures  may  not  be  necessary,  but  the  repair  may  be  post- 
poned to  a  more  favorable  time. 

The  upper  end  of  a  leak  in  a  masonry  dam  is  exceedingly 
difficult  to  find.  If  chopped  hay  or  sawdust  be  thrown  into 
the  water  over  where  the  leak  is  supposed  to  be,  it  will  often 
be  drawn  into  the  opening,  sometimes  stopping  the  leak,  but 
at  least  indicating  its  location  when  the  water  is  drawn  down. 
The  same  plan  may  be  adopted  in  the  case  of  an  earth 
embankment;  but  a  leak  in  this  is  generally  apparent,  having 
a  funnel-shaped  opening  in  the  reservoir.  It  may  be  possible 
to  locate  the  horizontal  zone  in  which  the  leak  exists  by 
emptying  the  reservoir  and  refilling  it  slowly,  noting  at  what 
elevation  of  water  the  leakage  again  begins. 

A  leak  in  the  masonry  is  generally  repaired  by  thoroughly 
cleaning  the  opening,  forcing  rich  Portland-cement  mortar 
into  it  until  it  is  completely  filled,  and  plastering  the  face  of 
the  wall  with  the  same.  If  there  is  a  general  leakage,  it  will 
be  well  to  clean  the  wall  thoroughly  and  face  it  with  4  to  6 
inches  of  concrete,  plastered  with  rich  cement-mortar.  A 
leak  can  never  be  repaired  from  the  down-stream  side,  but 
only  from  the  up-stream  or  water  side. 

A  leak  in  an  embankment  may  be  very  troublesome  to 
stop.  If  it  be  small,  forcing  sand  and  clay  into  the  hole, 
together  with  a  little  water,  maybe  effective;  or  the  upper 
end  of  the  opening  may  be  enlarged  and  compactly  filled  with 
dry  puddling  material  well  mixed  and  then  moistened  slowly, 
sheet-piling  being  in  some  cases  driven  across  the  opening, 
extending  several  feet  on  each  side  of,  below,  and  above  it,  the 
puddle  being  compacted  behind  this  and  good  embankment 
material  in  front  of  it.  The  permanent  stoppage  of  a  leak 
will  sometimes  require  that  a  V-shaped  cut  in  the  embank- 


490  WATER-SUPPLY  ENGINEERING. 

ment  be  made  down  to  the  leak,  and  refilled  with  the  best  of 
material  thoroughly  puddled  as  dry  as  possible. 

Loss  of  water  by  evaporation  can  generally  be  decreased 
only  by  reducing  the  area  of  the  water-surface;  although  it 
is  possible  that  a  high  board  fence  around  a  small  reservoir 
would  have  this  effect  by  shutting  off  the  wind,  and  it  at  least 
would  serve  to  keep  leaves  out  of  the  reservoir  to  a  large 
extent.  The  exposed  water-surface  can  be  reduced  in  many 
cases  by  draining  all  ponds  on  the  watershed,  and  storing  no 
water  except  in  the  reservoir;  and  all  watercourses  should  be 
kept  clear  and  open  for  the  same  reason. 

The  slopes  of  the  watershed  are  in  their  most  desirable 
condition  when  covered  with  sufficient  vegetation  to  prevent 
rapid  evaporation  and  erosion  of  the  soil,  but  of  such  character 
and  amount  as  will  extract  the  least  amount  of  moisture  in 
their  growth.  Slowly  growing  trees  seem  to  meet  this 
requirement,  while  weeds  and  other  plants  of  rapid  growth 
deplete  the  ground-storage  unnecessarily. 

It  is  not  sufficient  to  get  the  maximum  amount  of  water 
into  the  reservoir  as  quickly  as  possible,  and  to  prevent  loss 
of  this  by  leakage;  but  that  lost  over  the  spillway  should  be 
reduced  to  a  minimum,  and  that  stored  should  be  used  to  the 
best  advantage.  The  first  requirement  is  met  if  all  distribut- 
ing-reservoirs be  full  when  heavy  downpours  occur.  The  use 
of  flash-boards  in  the  spillway  is  recommended  only  in  extreme 
cases,  and  even  then  they  should  be  so  made  as  to  break  or  in 
some  way  automatically  and  without  fail  be  removed  before 
the  water  rises  to  a  distance  below  the  top  of  the  embank- 
ment equal  to  the  maximum  wave-height. 

Economy  in  use  can  be  partially  controlled  from  the 
distributing-reservoir  if  there  be  one,  or  otherwise  from  the 
storage-reservoir,  by  regulating  the  amount  of  water  admitted 
to  the  distribution  system.  If  this  be  less  than  the  normal 
consumption,  the  upper  part  of  the  conduit  will  be  only  partly 


J^ESEJiVOlKS,  HEAD-WORKS,   AND    INTAKES.  49 1 

filled,  the  head  will  consequently  be  reduced  and  the  flow 
from  each  fixture  become  less.  In  such  a  case  arrangements 
should  be  made  for  instantly  opening  the  gates  at  the  reservoir 
and  obtaining  full  head  in  case  of  fire.  Other  methods  of 
regulating  consumption  will  be  considered  in  Art.  iio.  If 
the  reservoir-bottom  is  not  already  so  graded  as  to  completely 
drain  from  all  parts  to  the  outlet  and  thus  utilize  all  the  water 
stored,  the  first  opportunity  should  be  taken  for  effecting 
this.  Probably  the  greatest  opportunity  for  economy  occurs 
in  selecting  the  times  for  necessary  wasting  of  water,  as  in 
cleaning  the  reservoir,  removing  water  from  the  stagnant 
layer,  etc.  These  should  be  selected  at  the  beginning  of  a 
season  during  which  the  yield  exceeds  the  consumption;  for 
if  before  this,  the  ordinary  supply  cannot  be  fully  provided 
until  this  season  begins;  and  if  after,  all  surplus  yield  between 
the  beginning  of  this  season  and  the  emptying  of  the  reservoir 
is  lost. 

The  storage-reservoir  is  designed  to  supply  the  deficiency 
due  to  a  certain  dry-weather  rate  of  consumption.  When  the 
consumption  is  found  to  be  exceeding  this  rate,  additional 
storage  should  be  provided;  unless  the  rate  can  be  reduced 
by  some  method.  As  a  check  upon  the  original  calculations, 
and  an  aid  in  preparing  plans  providing  for  increased  con- 
sumption, one  or  more  rain-gauges  should  be  maintained  upon 
the  watershed,  and  the  daily  evaporation  at  the  reservoir 
measured.  It  is  desirable  also  to  obtain  the  temperature  and 
humidity  of  the  air,  and  velocity  and  direction  of  the  wind, 
to  assist  in  studying  the  run-off  phenomena.  A  daily  record 
of  the  height  of  water  in  the  reservoir  should  be  kept,  and 
the  increase  of  height  due  to  each  storm  should  be  noted. 
An  accurate  topographic  map  of  the  reservoir  should  be  had, 
and  from  this  the  cubic  feet  of  water  corresponding  to  each 
foot  of  elevation  ascertained;  a  table  showing  these  being 
prepared  for  convenient   use.      During  rainless  weather    the 


492  WATER-SUPPLY  ENGIXEERING. 

drop  in  the  reservoir  will  indicate  the  consumption  plus 
evaporation  and  seepage,  and  the  latter  should  be  known  that 
they  may  be  deducted  to  give  the  consumption. 

There  are  many  reasons  why  such  calculations  of  con- 
sumption can  seldom  be  accurate,  and  it  is  desirable  to 
provide  a  meter  on  the  supply-main  near  the  reservoir.  On 
any  but  the  smallest  systems  the  Venturi  meter  is  probably 
the  one  best  adapted  for  this  purpose.  The  reading  of  this 
should  be  recorded  at  least  once  a  day,  and  twice  a  day  is 
preferable,  particularly  if  there  be  no  distributing-reservoir. 

Art.  105.     Prevention  of  Deterioration  or 
Destruction. 

Watersheds  should  be  preserved  from  erosion  by  the 
run-off,  reliance  being  placed  mainly  upon  vegetation. 
Streams  and  rivulets  should  not  be  permitted  to  erode  their 
banks  and  beds;  the  use  of  loose-stone  or  brush  dams  to 
decrease  velocity,  and  of  facines  or  of  slope-walls  of  field  stone 
to  protect  the  banks,  being  preventives  which  are  generally 
applicable. 

Slope-walls  around  the  reservoir  should  be  maintained 
intact,  and  no  vegetation  should  be  permitted  to  grow  in 
their  interstices.  Roads  and  walks  should  be  kept  weeded 
and  neat  in  appearance,  nothing  so  inviting  vandalism  and 
petty  damages  as  apparent  neglect  of  appearances  on  the  part 
of  the  authorities.  All  gates,  valves,  and  other  machinery 
should  be  tested  frequently  to  insure  their  serviceability  if 
suddenly  called  upon;  and  advantage  should  be  taken  of 
every  opportunity  to  examine,  lubricate,  and  otherwise 
maintain  in  the  best  condition  all  valves,  screens,  sluice-gates, 
etc. 

The  tops  of  no  embankments  should  be  permitted  to 
settle  below  their  designed  elevation,  but  should  be  immedi- 


JHESEKP'OI/iS,  HEAD-WORKS,  AND    INTAKES.  493 

atelj'  raised  to  this  with  good  material  if  any  settlement 
occur.  Low  spots  in  the  banks  have  caused  the  destruction 
of  more  than  one  reservoir  by  floods.  The  outer  slopes  of 
the  banks  should  be  kept  sodded  or  paved  to  prevent  rain 
from  washing  gullies  in  them.  Gutters  and  drains  on  the 
berme  should  be  kept  open.  Sodded  slopes  should  be  mowed 
occasionally  to  encourage  the  growth  of  a  thick  protective 
sod. 

The  available  area  of  the  spillway  should  never  for  a  day 
be  in  any  way  diminished,  unless  temporarily  when  water  in 
the  reservoir  is  low.  The  channel  below  the  spillway  should 
be  so  confined  and  kept  clear  that  no  waste-water  can  wash 
the  foot  of  an  embankment  or  in  any  way  endanger  its  safety. 

Art.  106.     Intakes,  Wells,  etc. 

Intakes  generally  require  little  attention  beyond  excluding 
or  removing  stoppages  at  their  outer  ends.  Fish,  sticks,  and 
floating  matters  are  occasionally  caught  in  the  screen,  and 
require  to  be  removed.  But  the  greatest  trouble  is  that 
experienced  with  anchor-,  needle-,  or  slush-ice.  This  collects 
around  some  intakes  to  such  an  extent  as  to  completely  close 
them  and  stop  all  pumping,  and  is  caused  by  needles  of  ice 
which  are  so  tossed  about  by  rough  water  as  to  prevent  their 
cohering  into  a  sheet.  The  motion  of  water  towards  the 
intake  draws  these  needles  with  it,  where  they  collect  and 
freeze  into  a  more  or  less  solid  mass.  They  never  occur  in 
still  water,  and  seldom  on  a  windward  shore.  The  most 
feasible  method  of  preventing  their  entering  the  intake  is  to 
make  this  opening  so  large  that  the  velocity  of  flow  towards 
it  is  not  sufificient  to  draw  the  ice-needles  from  the  surface. 
They  have  been  prevented  from  entering  the  intake  by  use 
of  warm  air  or  steam,  as  described  in  Article  91.  At  a 
Chicago  intake,  during  the  winter  of   1898-9,  the  interior  of 


494  WATER-SUPPLY  ENGINEERING. 

the  intake-tower  wis  heated  by  steam-radiators  to  prevent  the 
formation  of  ice  therein.  If  the  intake  be  in  a  river-wall,  or 
intake-tower  rising  above  the  water,  needle-ice  may  often  be 
prevented  from  entering  the  opening  by  fastening  over  it  a 
raft  floating  upon  the  surface;  the  quiet  water  existing  under 
this  permitting  the  needles  to  freeze  together  and  to  the  raft. 
It  is  thought  this  method  was  first  used  in  Jersey  City,  where 
the  raft  was  made  of  12  X  12  timbers  and  was  four  times  the 
length  of  the  screen. 

Wells  seldom  freeze,  whether  deep  or  shallow,  the  tem- 
perature of  ground-water  seldom  falling  below  40°  to  45°, 
An  exception  occasionally  occurs  in  the  case  of  deep  non- 
artesian  wells,  some  of  which  "  breathe  "  or  take  in  air  when 
the  barometer  is  high  and  give  it  out  when  it  is  low  (owing 
to  the  existence  of  large  air-reservoirs  in  the  soil);  the 
inbreathing  in  cold  weather  resulting  in  freezing  the  pumps  if 
these  be  above  water,  together  with  so  much  of  the  suction 
and  delivery  as  are  not  under  water. 

The  main  difficulties  experienced  with  wells  are:  leaking 
of  air  into  the  well  or  collecting-pipe;  choking  of  the  well 
with  sand ;  and  decreased  yield,  which  is  frequently  due  to 
one  or  both  of  the  defects  just  mentioned,  but  in  most  cases 
to  other  wells  tapping  the  same  water-stratum,  in  which  case 
the  only  remedy  is  greater  suction  or  more  wells,  or  both. 
If  the  remedy  of  new  wells  is  adopted  it  is  desirable  to  drive 
them  to  a  new  water-stratum  if  such  can  be  found. 

Air  in  wells  or  collecting-pipe  and  the  remedy  have  been 
referred  to  in  Art.  92.  If  the  defect  be  in  a  well,  it  may  be 
located  by  closing,  one  at  a  time,  the  valves  between  the 
wells  and  the  collecting-pipe,  and  noting  when  air  ceases  to 
enter.  If  air  still  enters  when  all  wells  are  shut  off,  the  leak 
is  apparently  in  the  collecting-pipe,  and  this  must  be  uncovered 
(if  buried)  and  the  leak  stopped  by  repacking  and  tightening 
up  joints  if  these  be  flanged,  by  recalking  if  of  lead,  or  by 


KESEKVOIRS,  HEAD-WORKS,  AXD    INTAKES.  495 

calking  between  pipe  and  sleeve  at  each  joint  if  these  be 
threaded;  the  joints  being  afterward  thoroughly  coated  with 
hot  asphaltum. 

If  the  leak  be  in  a  well  it  cannot  generally  be  stopped, 
but  a  smaller  pipe  may  be  inserted  reaching  to  the  bottom  of 
the  well  and  connected  at  the  top  with  the  collecting-pipe, 
this  connection  replacing  that  with  the  defective  well. 

If  the  bottom  of  a  tube-well  become  filled  with  sand,  this 
may  generally  be  removed  by  a  "sand-bucket,"  a  "sand- 
pump  "  (working  somewhat  on  the  principle  of  the  steam- 
siphon),  or  by  washing  the  sand  up  through  the  well  to  the 
surface  by  the  use  of  the  water-pipe  of  the  jetting-down 
method  of  well-sinking.  The  latter  plan  also  tends  to  clear 
the  screen-openings  of  any  material  which  may  be  choking 
them;  but  if  the  soil  is  very  porous,  it  may  fail  to  be  effective 
because  of  the  loss  of  water  into  the  soil. 


CHAPTER    XIX. 
PUMPING-PLANTS   AND   FILTERS. 

Art.  107.     Pumping-plants. 

The  pumping-plant  is  the  heart  of  a  system,  and  this 
vital  part  should  be  put  in  charge  of  none  but  an  experienced 
and  faithful  man.  The  pumps  should  be  given  the  best  of 
care,  both  for  reasons  of  economy  and  because  of  the  serious- 
ness of  a  breakdown.  There  should  be  a  reserve  of  pump, 
engine,  and  boiler  power,  which  should  be  used  occasionally 
to  test  its  readiness  for  immediate  service  in  case  of  an 
emergency.  The  lack  of  such  reserve  has  often  resulted  in 
direct  money  loss,  owing  to  the  fact  that  the  pump  in  daily 
use  could  not  be  put  out  of  service  for  a  few  days  to  permit 
of  a  needed  overhauling,  and  hence  was  wrecked  when  its 
usefulness  might  have  been  preserved  for  many  years. 

The  **  slip  "  in  a  pump  increases  with  age,  and,  since  it 
reduces  the  amount  of  water  which  the  pump  can  lift,  may 
become  a  serious  matter.  It  is  one,  however,  which  it  is  not 
difficult  to  remedy,  and  the  slip  should  not  be  permitted  to 
become  excessive. 

Air  from  leaks  in  the  suction-pipe  causes  a  pump  to 
"pound"  and  thus  to  gradually  rack  itself  to  pieces.  This 
should  be  prevented  by  closing  such  leaks;  or,  if  this  is  found 
to  be  impossible,  by  placing  an  air-drum  on  the  suction-line 
and  removing  the  air  from  this  by  means  of  a  small  vacuum- 
pump. 

496 


PUMPING-PLANTS  AND    FILTERS.  497 

Sand  entering  a  pump  will  cause  it  to  cut  its  plunger  and 
plunger-ring,  and  to  increase  its  slip  rapidly.  If  sand  cannot 
be  kept  out  of  the  suction,  it  should  be  intercepted  before 
reaching  the  pump. 

Maintaining  the  efificiency  of  a  well-designed  plant  gen- 
erally requires  a  careful,  intelligent,  skilful  engineer,  provided 
with  the  proper  tools,  good  fuel,  and  water  which  deposits 
neither  scale  nor  mud  in  the  boilers.  Opportunity  should  be 
given  for  overhauling  each  engine  and  boiler  twice  a  year, 
either  by  excess  of  storage,  or  duplicate  pumping-plant,  or 
both.  The  overhauling  can  generally  best  be  done  in  the 
spring  and  fall,  when  the  consumption  is  lowest. 

The  main  problem  in  connection  with  the  pumping-station 
is  the  one  of  economj';  to  do  the  desired  pumping  at  the 
least  expense.  In  Table  No.  72  it  is  seen  that  in  the  cities 
cited  the  salaries  constituted  from  one  to  three  fifths  of  the 
total  cost  of  pumping,  assuming  the  cost  of  coal  at  %2  ;  and 
that  the  coal  used  amounted  to  from  two  to  three  fifths  of  the 
total  cost,  except  in  the  cases  of  the  high-duty  pumps  at 
Boston  and  Milwaukee,  where  it  constituted  31  and  39  per 
cent  respectively.  At  Newton,  Mass.,  in  1896,  the  coal-bill 
was  but  35  per  cent  of  the  total  expense  of  pumping, 
although  coal  cost  S4. 18  per  ton,  the  engines  developing  a 
duty  of  III  million  foot-pounds;  while  at  Woonsocket, 
R.  I.,  during  the  same  year  the  cost  of  coal  was  48  per  cent 
of  the  total  cost,  the  duty  of  the  engine  being  54  million 
gallons;  the  remaining  expenses  in  both  cities  being  almost 
exactly  the  same  per  million  gallons  raised  one  foot.  The 
cost  of  oil  and  stores  is  very  small;  that  of  repairs  also  is 
small  unless  the  engineer  be  careless  or  the  pumps  old  and 
well  worn;  the  number  of  men  employed  is  practically  fixed 
by  the  size  of  the  plant;  and  coal-consumption  offers  the 
chief  field  for  economy.  This  of  course  varies  with  the 
efficiency  of  the  plant  and  of  the  men  who  run  it,  the  quality 


498 


WATER-SUPPLY   ENGINEERING. 


Table 
cost  of  pumping 


Name  of  Station. 


Chicago:   North  Side. 

West  Side.. 
Central.  .  .  . 
Lake  View. 

14th  Street. 

68th  Street. 

Whole  city 


Pittsburg  :   Brilliant  Station 

Philadelphia:   Fairmount  Station 

Spring  Garden 

Belmont • 

Roxborough,  Main 

"  ,  Auxiliary.. 

Frankfort 


Boston:  Chestnut  Hillf. 


Mystic 

Louisville:  Station  No.  i,    E  engine 

"      I,  W       "       

"    I,  W      "      .... 

"     I,  N        "      .... 

New  Station,  No.  3  engine.. 

River-bank  pumps 


Combined  operations. 


Cleveland  :   Division  Street 

Fairmount 

Milwaukee  :   North  Point 

High-service  engines  . 

Combined  operations. 


U  2 
rt  II 


43.707 

32.489 
15.005 

9.297 
17,829 

22,595' 


140,920 
114,118 


98,388 
27.584 
38,704 

16,278 
4,210 
9,188 


13,315 

62,316 
2,223 

12,211 
1,648 


13.859 


o  -O 


22,544 

19,271 

11.359 
4,600 

15,501 
i2,8Si 


86,156 

14,184 
9,912 

39,096 

6.361 

5,222 

16 

4,107 

3. 511 

4.074 
1,082 
1,124 

311 

224 

2,144 

7 


4.891 

15,390 

639 

9,116 

1.934 


a  . 


« 


a<  c  _ 

V  rttt. 


108.6 

104.2 
105. 1 
108.0 

120.4 

133-5 


113. o 

400.0 
100. o 
150.6 
220.4 
349-0 
83.2 
209.9 

126.7 

149.4 
174-7 
173-9 
175-8 
175-8 
179.1 
iSi.i 


176.6 

192.6 

162.4 

161. 7 

80.8 


11,051 

FROM    REPORTS 


Attleboro,  Mass. 
Bay  City,  Mich. 
Newton,  Mass.  . 
Oberlin,  Ohio. . . 
Yonkers,  N.  Y. . , 


456.9 
3.535-8 
1,592.8 

290.0 
4.309-5 


II5-6 
1,909.5 

666.3 

24.6 

1,243.2 


I75and  188 

113 

254 

So 

200  ± 


A    Anthracite;  B,  Bituminous.     *  Coal  equivalent  to  oil  burned;  i  gallon  of  oil  assumed  as 
equal  to  10.435  lbs.  of  coal,  corresponding  to  14  lbs.  evaporation  for  oil,  and  8.75  lbs  for  coal; 


PUMPING  PLANTS   AND    FILTERS. 


499 


No.  72. 

IN    TWELVE    CITIES    IN    1893. 


°.  a 

Coal  used  per 
Million  Gallons 
per  Foot  Head, 
Pounds. 

V  («  0 

>  0  a 

< 

Comparison  of  Cost,  in  Cents,  of  Pumpage  per 
Million  Gallons  per  Foot  Head,  on  Uniform 
Basis  :   Head  =  200  feet;  Coal  at  %i  per  ton. 

Salaries. 

Oil  and 
Stores. 

Mainte- 
nance and 
Repairs. 

Coal. 

Total 
Cost. 

46.7 

51-5 
64.4 
44.6 

87.3 
63.5 

17.840 

16.180 
12.560 
18.720 

9.560 

13.140 

j  $5,69A  \ 
\    3-07B  f 

2.82 

3.10 

3-15 
(    5.40A  ) 
1     3-i2Bf 

1. 106 

1.208 
1.464 
2.500 

1. 712 

1.708 

0.058 

0.048 
0.058 
0.170 

0.102 

0.086 

0.150 

0.192 
0.092 

1.784 

1. 618 
1.256 
1.872 

0.956 
I  314 
1.448 
2. on 

3.098 

3.066 

2.870 
4-542 

2.924 
3-174 

0.154 
0.066 

57.6 
41-5 

14.480 

20.114 
Water  Power 
16.710 
19.676 
21.222 

18.880 

9.464 

15.097 

1.467 

1.048 
O.411 
0.655 
1.227 
1.300 

1.226 

1.673 
1.346 

0.075 

0.134 
0.025 
0.051 
0.080 
0.203 

0.154 

0.097 

0.106 

0.132 

0.340 
O.2S6 
0.577 
0.577 
0.853 

1.088 

O.2S3 

0.442 

3.122 
3-533 

1. 12 

49.9 
42.4 
39-3 

44-2 

88.1 

55.2 
48.4 
48.0 

24-3 
25.2 
92.6 

26  8 

1-73 
1-73 
2.04 

1.74 
(    4-75  ) 

to      B 
(    5.30) 
4.12104.45 

1. 671 
1.968 
2.122 

1.888 

0.946 

1. 510 

2-954 
3.852 
4.478 

4.356 

3.000 

3-404 

l.626t 

1.329 
3.217 
1. 121 
2.246 

0.147 

0.104 
0.269 
0.098 
0.393 

0.636:!: 

0.281 
0.378 
O.0S2 
0.065 

1-542 

2.102 
2.142 
0.822 
1.054 

54.1 

39-7 

38.9 

100.6 

79.1 

15.418 

21.018 

21.422 

8.220 

10.544 

2.42 

1.42 
i.i9± 

5.45A 
5.45A 

3-9S4 

-3.816 
6.006 
2.123 

3.758 

98.1 

8.50 

5-45 

1. 318 

0.150    '    0.079 

0.850 

2-397 

FOR    1896. 

Cost  per  Million  Gallons  Raised  i  Foot  High. 

4.60 

4-77 
4.18 
2.25 
4-13 

Station  Expenses. 

Total  Maintenance. 

39-75 

III.OO 

5.66 

$0.0996 
.064 
.05 
.61 

riec  + 

$0,765 

0-393 

0.63 

2.38 

-'•' 

oil  at   t\  cts.  per  gallon,     t  Evaporation  equals  n  ()\       %  Above  the   usual  cost.     The  total 
should  be  about  3.23,  according  to  Mr.  Charles  Hermany,  Supt. 


500 


fVATER-SUPPLY  ENGINEERING. 


of  the  coal,  the  amount  pumped,  and  its  relation  to  the 
capacity  of  the  pumps  and  boilers. 

The  cost  of  pumping  in  seven  large  cities  in  18^-3  is  given 
in  Table  No.  72  (by  S.  G.  Artingstall,  before  the  Am. 
W.  W.  Ass'n,  May  1895). 

For  smaller  plants  the  cost  is  generally  greater.  At 
Newton,  Mass.,  it  was  4.9  cents  per  million  gallons  raised 
one  foot,  in  1894;  3.9  cents  in  1895,  5  cents  in  1896,  and 
5  cents  in  1897.  At  Taunton,  Mass.,  it  was  10.44  cents  in 
1893,  15.5  cents  in  1895,  and  15.67  cents  in  1896.  At 
Montreal  it  has  varied  between  37.6  and  7.8  cents  in  fourteen 
years,  averaging  19.5  cents.  The  following  shows  the  cost 
of  raising  1,000,000  gallons  one  foot  high  in  several  New 
England  systems. 


T3 

0 

t) 

0 

Si 

< 

C 
0 

ffl 

c 
c 

•a 

n 
2; 

c" 

0 

3 

0 

e 

bi 
c 

•a 

c 
0 

c 

3 

S 
la 

0 

0 

c 
0 
0 

I8qs 

9.27 

17.2 

3-66 

17-4 

5-30 

3-9 

22.3 

14.7 

15-5 

10.5 

6.3 

1896 

9.96 

II. 8 

3-99 

16.0 

4.29 

5.0 

23.2 

18. 1 

15-7 

b.3 

b.2 

The  plan  of  offering  a  bonus  to  the  fireman  and  engineer 
for  every  million  foot-pounds  by  which  the  duty  exceeds  a 
certain  amount  has  much  to  recommend  it,  since  their  care- 
fulness and  efficiency  form  a  large  factor  of  the  duty  obtained 
from  a  given  plant. 


Art.  108.     Operating  Filters. 

The  maintenance  of  mechanical  filters  is  a  very  simple 
matter  when  the  water  is  of  uniform  quality — as  ground-water 
generally  is;  requiring  only  that  for  a  given  quantity  of 
water,  as  registered  by  a  meter  or  by  the  engine-counter,  a 
fixed    amount    of    chemical    be    added,    which    is    generally 


PUMPING-PLANTS   AND   FILTERS.  $01 

performed  automatically;  and  that  after  a  certain  amount  has 
passed  the  filter  this  should  be  cleaned  by  opening  and  closing 
a  few  valves. 

If  the  water  be  from  a  river,  however,  the  condition  is 
different,  and  care  must  be  taken  to  so  proportion  the 
chemicals  to  the  amount  treated  that  the  desired  purification 
is  obtained,  but  without  waste  of  chemicals  or  permitting 
these  to  enter  the  effluent  in  injurious  quantities.  For  this 
purpose  it  is  desirable  to  make  a  chemical  analysis  of  the 
water  at  least  once  a  day,  and  more  frequently  if  changes  in 
it  be  rapid.  If  the  water  carry  any  considerable  amount  of 
matter  in  suspension,  the  test  for  this  (by  platinum  wire  or 
otherwise)  should  be  made  at  least  twice  a  day,  and  the 
coagulant  regulated  accordingly.  The  daily  chemical  test  of 
the  crude  water  should  be  accompanied  by  one  of  the  effluent. 
Once  or  twice  a  month  tests  should  be  made  of  samples  taken 
hourly  throughout  the  day,  as  the  river-water  may  be  affected 
by  manufacturing  wastes  discharged  at  certain  hours  of  the 
day,  or  by  other  periodic  pollution. 

At  the  beginning  of  the  operation  of  a  filter-plant  it  is 
of  course  necessary  to  make  continuous  tests  of  both  crude 
and  filtered  water,  and  meantime  to  vary  the  amount  of 
coagulant  until  it  has  been  learned  what  amount  gives  the 
best  result  with  each  condition  of  water.  From  these  experi- 
ments a  table  can  be  prepared  showing  at  a  glance  what 
amount  of  coagulant  is  desirable  if  the  chemical  analysis  be 
known.  If  at  any  time  the  daily  or  hourly  tests  indicate  that 
the  desired  purification  is  not  being  attained,  this  study 
of  relations  between  condition  and  treatment  should  be 
repeated. 

Many  filtration-plants  are  run  without  such  analyses  being 
made,  the  only  test  being  the  appearance  and  taste  of  the 
water.  But  such  a  lack  of  method  is  almost  sure  to  result  in 
low  efficiency,  with  probably  as  great  or  even  greater  expense 


502  WATER-SUPPLY  ENGINEERING. 

for  coagulant  than  is  necessary  for  good  results;  and  justice 
to  the  consumers  demands  better  water  than  they  receive 
from  plants  so  run. 

The  cost  of  running  a  mechanical-filter  plant  will  be  that 
of  chemicals  and  of  labor.  Alum  suitable  for  use  as  a 
coagulant  costs  about  $27  per  ton.  The  labor  for  a  small 
plant — 500,000  to  750,000  gals,  per  day — can  generally  be 
performed  by  the  pumping  engineer.  For  larger  plants  prob- 
ably one  man  for  every  three  to  five  million  gallons  will  be 
necessary.  The  life  of  a  plant  cannot  be  stated,  as  the 
modern  mechanical  filter  is  but  a  very  few  years  old. 

The  maintenance  of  an  English  filter  includes  regulation 
of  the  rate  of  filtration,  cleaning  of  the  beds,  washing  and 
replacing  the  sand  ;  and  removing  ice  if  the  filter  is  uncovered. 
The  basin  of  the  filter  should  need  no  repairs  or  attention; 
but  the  sand  will  need  to  be  renewed  from  time  to  time. 
Analyses  should  be  made  of  the  crude  and  filtered  water, 
as  in  the  case  of  mechanical  filters,  and  these  should  be 
taken  daily  for  each  bed.  If  the  efficiency  from  any  bed 
becomes  low,  the  rate  of  filtration  should  be  reduced,  or  the 
bed  examined  for  "  blow-outs,"  or  holes  in  the  sand  per- 
mitting the  free  passage  of  water.  Water  sometimes  follows 
the  walls  down,  and  reaches  the  drains  without  having  been 
filtered.  This  should  be  prevented  by  making  the  walls  as 
rough  as  possible,  by  building  horizontal  ledges  in  them  a 
short  distance  above  the  bottom,  or  by  banking  the  sand 
against  them  all  around. 

The  beds  are  generally  cleaned  with  wide,  square-pointed 
shovels,  and  but  one-quarter  inch  to  two  inches  of  sand 
removed  at  a  time.  The  men  should  not  stand  behind  the 
shovels,  but  at  one  side,  and  should  not  walk  upon  any  part 
of  the  bed  which  has  been  cleaned.  If,  however,  the  sand 
has  become  considerably  clogged  by  long  use,  this  precaution 


PUAfPIAG-PLANTS  AND   FILTERS.  503 

is  not  necessary,  as  it  should  be  worked  over  with  a  garden- 
fork  after  cleaning,  and  levelled  off  with  a  rake.  This  is 
made  necessary  by  the  fact  that  in  time  a  gelatinous  film  and 
fine  silt  work  their  way  through  the  entire  bed,  and  bind  the 
sand  particles  together.  When  this  clogging  reaches  within 
6  or  8  inches  of  the  bottom  of  the  sand,  the  whole  of  this 
should  be  removed  and  washed. 

If  there  is  any  ice  upon  the  water  in  the  filter  before 
cleaning,  this  should  be  removed.  During  use,  if  water  be 
kept  continually  a  foot  or  more  deep  above  the  sand,  the  ice 
is  not  particularly  objectionable  if  it  do  not  injure  the  walls 
or  banks  of  the  filter-basin  or  other  structures.  After  the 
ice,  if  any,  is  removed  the  water  is  drawn  off  of  the  surface 
of  the  filter  and  down  to  six  inches  below  it  (means  should  be 
provided  for  this).  Scraping  is  then  completed  as  rapidh- 
as  possible  and  the  filter  refilled  and  put  into  service  again. 
The  refilling  is  generally  done  from  the  bottom,  but  in  some 
cases  from  the  top;  the  objection  to  the  latter  method  being 
the  washing  of  the  surface  caused  by  water  flowing  over  the 
uncovered  sand.  When  filled  from  the  bottom,  filtered  water 
should  be  used  and  the  sand  covered  with  this  6  inches  or 
more  deep. 

Cleaning  should  be  done  in  fair  weather,  neither  freezing 
nor  very  hot;  and  the  sand  should  be  moist,  but  not  wet. 
If  the  sand  freeze,  it  is  of  course  practically  impossible  to 
remove  the  desired  thin  layer.  If  the  sun  be  too  hot,  the 
gelatinous  matter  and  silt  bake  into  a  cake,  nearly  as  difficult 
as  ice  of  treatment.  Rain  falling  upon  a  cleaned  surface  will 
so  compact  and  wash  it  as  to  make  it  necessary  to  fork  and 
rake  it  before  a  desirable  rate  of  flow  is  obtained.  The  dis- 
advantages of  ice  and  rain  are  avoided  by  covering  the  filter. 

The  sand  removed  is  washed  or  thrown  away,  whichever 
is  cheaper.  After  being  washed,  it  is  generally  stored  until 
the    thickness    of   the    sand- bed    has    been     reduced    to    its 


504  WATER-SUPPLY  ENGINEERING. 

minimum  limit,  when  all  the  sand  is  replaced  upon  the  bed. 
After  some  years  of  use  the  sand  grams  seem  to  become 
rounded  and  the  rate  of  filtration  possible  decreases,  until  it 
becomes  necessary  to  obtain  new  sand  throughout. 

Washing  is  done  in  a  number  of  ways:  by  piling  up  the 
sand  and  simply  turning  a  hose  upon  it;  by  washing  it 
through  a  sluice  having  strips  nailed  across  the  bottom,  the 
sand  collecting  behind  the  strips  while  the  water  carries  the 
silt  past  them ;  by  revolving  cylinders  of  different  kinds  in 
which  the  sand  is  placed  and  through  which  water  is  passed; 
by  hoppers,  either  single  or  in  series,  the  sand  falling  into  the 
hopper  from  above,  while  a  stream  or  jet  of  water  enters  it 
from  the  smaller  bottom  opening,  the  water  overflowing  the 
hopper  and  carrying  the  silt  with  it,  while  the  sand  falls  into 
another  hopper  or  is  piled  up  for  future  use. 

A  bed  is  cleaned  whenever  the  maximum  head  possible 
or  desirable  fails  to  force  through  it  the  desired  amount  of 
water.  This  may  vary  from  three  or  four  days  to  as  many 
months  in  the  same  plant;  depending  upon  the  amount  of 
clay  or  loam  carried  by  the  river  and  the  length  of  time  the 
sand  has  been  in  use.  If  cleaning  is  required  oftener  than 
once  in  three  or  four  weeks  with  clear  water,  the  efficiency 
of  the  plant  as  well  as  economy  would  require  an  entire 
renewal  or  cleaning  of  the  sand.  If  the  muddiness  of  the 
river  compels  cleaning  oftener  than  this,  sedimentation-basins 
should  be  provided ;  unless  such  a  condition  lasts  for  but  two 
or  three  weeks  in  the  year,  and  even  then  they  are  desirable. 

At  Poughkeepsie  one  man  cleans  about  150  square  feet 
of  filter  per  hour,  including  removing  the  sand  from  the  bed, 
and  forks  and  rakes  500  square  feet.  Washing  the  sand  by 
a  double  hopper  costs  about  24  cents  per  cubic  yard,  the 
water  used  being  about  eighteen  times  the  amount  of  sand 
washed.  Hazen  gives  the  average  cost  of  washing  sand  by 
machinery  as  30  to  40  cents  per  cubic  yard;  and  140  to  170 


PUMrn\'G-PLANTS   AND    FILTERS.  505 

square  feet  per  hour  as  the  amount  of  filter  one  man  can 
scrape.  At  Lawrence,  Mass.,  300  cubic  feet  of  water  are 
used  for  washing  a  cubic  yard  of  sand,  or  about  I  I  to  I. 
The  cost  of  removing  ice  from  this  filter  during  1897  was 
S2323,  or  $930  per  acre.*  The  entire  cost  of  maintenance  at 
Lawrence  was  S7.70  per  million  gallons  filtered;  at 
Poughkeepsie  it  was  a  little  less  than  S3.  At  Ilion,  N,  Y., 
the  cost  of  cleaning  is  about  $0.82,  and  at  Hudson  §0.88,  per 
million  gallons.  These  figures  cannot  be  compared,  however, 
since  some  include  all  running  expenses  and  probably  interest 
on  the  cost  of  the  plant  also.  It  is  thought  that  %\o  per 
million  gallons  filtered  should  be  an  ample  allowance  for  one 
million  gallons  or  more  per  day;  this  sum  including  interest 
on  the  cost  of  the  filter-beds  and  sedimentation-basins,  as  well 
as  of  daily  chemical  analyses  and  proper  and  intelligent 
supervision. 

If  no  sedimentation-basins  or  filters  are  provided  for  a 
river-supply,  the  manager  of  the  water-works  should  use 
foresight  and  ingenuity  to  exclude  muddy  water  from  the 
distribution  system.  The  reservoirs  should  be  kept  filled 
while  the  water  is  clear,  and  pumping  discontinued  while  the 
river  carries  much  silt.  Two  reservoirs  should  always  be 
provided;  or  one  made  into  two  by  a  dividing  wall.  While 
the  river-water  is  roily  the  supply  should  be  drawn  from  one 
basin  only,  and  when  this  is  empty  it  may  be  filled  with  roily 
water,  which  is  allowed  to  clarify  itself  by  sedimentation 
while  the  supply  is  drawn  from  the  other  basin.  The  pumps 
should  be  at  least  capable  of  supplying  the  entire  maximum 
daily  consumption  in  twelve[hours;  then  by  working  24  hours 
per  day  in  filling  a  reservoir  with  muddy  water,  one  half  or 
more  of  the  time  occupied  in  emptying  the  other  reservoir 
can  be  given  to  sedimentation.  Water  can  be  greatly 
improved  by  sedimentation  in  this  way,  but  filtration  is  much 
to  be  preferred,  and  should  be  obtained  if  possible. 

*  See  Appendix  C. 


CHAPTER   XX. 


PIPES   AND    CONDUITS. 


Art.  109.     Maintaining  Quality  of  Water. 

After  entering  the  conduits  water  often  undergoes 
changes  in  chemical  composition,  and  generally  in  tempera- 
ture. The  latter  is  more  uniform  nt  the  taps  than  in  the 
reservoirs.      Fig.   91  shows   the  mean   temperature   for   four 


70° 

^ 

^ 

o*/j 

"^^ 

'ws 

65 

*/ 

/*■ 

4" 

JOM~ 

^?^ 

SZ 

' 

r\ 

66 

'/W 

\\ 

*/ 

*     TEMPERATURE  OF  WATER 
IN  BOSTON  RESERVOIR  AN 

T 

[^ 

40 

% 

/ 

p 

^'^ 

\ 

^^ 

-^ 

AVERAGE  OF  WEEKLY  OBSERVATIONS 
FOR  THE  YEARS  1891-5 

1             1 

3§ 

JAN. 

FEB. 

MAR. 

*PR. 

JUNE|JULY   AUG  |Sept*|oct.1nov 

DEC. 

Fig.  91. — Temperature  of  Water  in  Pipes. 
(From  paper  by  Geo.  C.  Whipple,  before  N.  E.  W.  W.  Ass'n.) 

years  in  a  Boston  reservoir  and  the  mains  fed  by  it,  Park 
Square  being  five  miles  from  the  reservoir,  and  Mattapan 
eleven  miles. 

If  the  water  in  the  mains  contain  organic  matter,  the 
decomposition  of  this  probably  will  continue  to  a  certain 
extent ;  but  the  chief  chemical  changes  will  be  those  due  to 
the  taking  into  solution  of  zinc  and  lead  from  service-pipes, 
as  already  referred  to.     Before  a  given  supply  is  used  tests 

506 


PIPES  Ah'D    CONDUITS. 


507 


should  be  made  to  ascertain  whether  these  metals  are  dissolved 
by  it,  and  if  they  are,  the  use  of  pipes  containing  them  should 
not  be  permitted  in  connection  with  the  system. 

The  chemical  changes  in  organic  matter  tend  to  purify 
the  water,  and  for  this  reason  a  purer  water  is  frequently 
found  at  a  distance  from  than  in  the  reservoirs.  It  is  generally 
found  also  that  water  is  purer  in  the  high  than  in  the  lower 
parts  of  the  city.  In  Boston,  for  five  years  from  1891-95, 
the  following  number  of  standard  units  of  organic  and  amor- 
phous matter  per  cubic  centimeter  was  found  at  the  points 
stated: 


Number  of  Standard  Units  per  cc. 

Organisms. 

Amorphous  Matter. 

Chestnut  Hill  Reservoir,  gate-house 

Rrookline                  "                    "              

248 
215 
194 

84 

209 
212 
190 
105 

'   Mattapan 

The  reduction  seems  to  occur  in  the  smaller  pipes.  From 
November  to  April  the  reduction  in  the  pipes  was  44  and  24 
per  cent  respectively;  and  from  May  to  October  it  was  62 
and  53  per  cent.  Bacteria  decreased  from  o  to  60  per  cent 
between  August  and  April,  and  increased  o  to  60  per  cent 
between  April  and  August,  when  the  most  organisms  are 
dying  in  the  mains.  Some  organisms  settle  out,  some  break 
up,  die  in  the  dariv,  and  are  devoured  by  sponges.  A  16-inch 
main  in  Boston  was  found  to  contain  a  lining  of  sponges  and 
polyzoa  \  inch  thick,  as  well  as  snails,  mussels,  and  countless 
infusoria.  The  animal  organisms  depend  upon  algse  and 
infusoria  for  food.  Chicago  was  last  year  troubled  with 
countless  numbers  of  snails  in  the  intake  and  mains.  Prob- 
ably all  surface-water  systems  contain  such  organisms  in  their 
pipes,  but  so  long  as  the  animal  organisms  are  sufficient  in 


5o8  WATER-SUPPLY  ENGINEERING. 

number  to  destroy  all  vegetable  and  dead  animal  matter  no 
harm  need  result.  It  is  thought  that  these  organisms  are  not 
found  in  ground-water  systems. 

The  life  of  the  animal  scavengers  in  a  system  seems  to 
require  a  circulation  of  water  past  them,  and  in  dead-ends 
amorphous  matter  generally  accumulates  and  contaminates 
the  water.  To  prevent  this,  water  should  be  frequently 
drawn  out  of  all  dead-ends,  thus  providing  circulation  and 
also  removing  putrefying  matter.  Deposits  of  mineral  sedi- 
ment also  collect  in  dead-ends  and  should  be  flushed  out.  It 
should  be  the  duty  of  some  one  employe  to  flush  out  each 
dead-end  at  stated  intervals,  and  keep  a  record  of  the  date 
each  one  is  flushed. 

But  little  sand  or  gravel  should  find  entrance  to  an  irriga- 
tion-conduit, the  head-gates  being  utilized  to  exclude  it  (see 
Art.  103).  Some,  however,  may  enter  during  floods,  and 
open  conduits  often  receive  considerable  sand  blown  in  by 
the  wind,  during  the  sand-storms  of  our  Western  plains. 
This  sand  is  generally  intercepted  by  a  sand-box  or  sand-trap, 
which  should  be  inspected  daily,  and  flushed  out  whenever 
the  sand  rises  within  a  foot  of  the  conduit. 

Art.  110.     Maintaining  Quantity  of  Water. 

It  is  the  function  of  a  conduit  and  distribution  system  to 
distribute  to  consumers  through  regular  appurtenances  all  the 
water  which  enters  their  furthest  end,  and  to  deliver  it  at  the 
desired  rate.  This  is  interfered  with  by  any  leaks,  breaks, 
or  other  losses;  or  by  contraction  of  the  channel  due  to 
deposits  or  other  accidental  stoppages,  by  the  closing  of 
gates,  or  by  reduction  of  pressure  in  the  pipes.  Under  this 
head  are  included,  therefore,  the  detecting  and  repairing  of 
leaks  and  breaks;  the  removal  of  deposits  and  accretions; 
thawing  of  frozen  pipes;   the  regulation  of  gates,   pressure- 


PIPES   AND    CONDUITS.  509 

regulators,  service-cocks,  and  fire-hydrants,  etc. ;  and  in- 
cidentally regulation  of  the  consumption. 

In  clay  or  compact  loam,  leaks  in  water-pipes  will 
generally  make  themselves  evident  at  the  surface  immediately 
above  them,  unless  this  be  paved  with  water-tight  material, 
such  as  asphalt  or  any  pavement  on  a  concrete  foundation. 
In  sand  or  gravel,  however,  the  existence  of  a  leak  may  be 
unsuspected  for  years,  and  its  exact  location  be  almost  im- 
possible of  determination  when  its  existence  is  known.  In 
paved  streets,  also,  a  leak  makes  itself  known  in  adjacent 
cellars  or  basements,  if  at  all;  but  the  building  in  which  it 
appears  may  be  at  a  considerable  distance  from  the  leak. 
When  the  ground-surface  is  frozen  for  some  depth  the  effect 
may  be  similar  to  that  of  a  pavement.  On  steep  hills,  water 
from  a  leak  frequently  follows  the  pipe  for  some  distance, 
appearing  at  the  surface  where  a  flatter  grade  begins. 

Where  the  appearance  of  water  at  the  surface  indicates  a 
leak  which  is  found  or  thought  to  be  at  some  distance  from 
the  point  of  emergence,  its  location  can  be  more  exactly 
determined  by  so  closing  valves  as  to  shut  off  the  pressure 
from  different  sections  successively,  each  section  being  made 
as  short  as  the  location  of  the  valves  will  permit.  The 
evidence  of  leakage  will  generally  decrease  soon  after  the 
right  section  is  cut  out.  An  examination  of  the  valve-boxes 
will  often  be  sufficient  to  determine  the  location,  water 
standing  in  these  being  evidence  of  its  existing  in  the 
ground  at  that  point,  and  of  the  leak  being  up-grade  from 
there.  An  examination  of  fire-hydrants  also  should  precede 
more  extensive  investigation,  the  top  of  each  being  removed 
to  discover  whether  water  is  not  entering  the  barrel  from  a 
partly  open  valve  and  escaping  through  the  drip  into  the 
ground.  Where  the  ground  is  frozen  or  sealed  with  paving, 
openings  cut  through  this  at  intervals  directly  above  the 
pipe-line  will  often  permit  the  nearness  of  a  leak  to  become 


510 


WATER-SUPPLY  ENGINEERING. 


C^ 


f  FDOT 


H    I — I    1-^1— b^    r"i    I    I    I 


Fig.  92. — Deacon  Waste-water  Meter. 
(From  Trans.  Am.  Soc.  C.  E.,  Vol.  XXXIV). 


PIPES  AND    CONDUITS.  511 

evident.  If  valves  are  closed  in  making  the  investigation,  it 
is  of  course  best  to  make  this  at  night,  when  the  consumers 
will  be  least  inconvenienced.  If  the  leakage  is  considerable, 
it  can  often  be  detected  by  the  "  singing  "  of  water  passing 
a  valve  which  is  almost  closed,  all  other  valves  and  service- 
cocks  connected  with  the  section  being  closed.  Or,  in  place 
of  this  method,  a  Deacon  Waste-water  Meter  (Fig.  92)  may 
be  connected  to  the  pipe  at  both  sides  of  a  closed  valve,  all 
valves  and  service-cocks  being  closed,  and  any  leakage  will 
be  registered  by  the  meter.  The  Cole-Flad  Pitometer  has 
recently  been  used  in  New  York  and  other  cities  for  measuring 
the  flow  in  mains  and  thus  locating  waste  and  leakage,  offering 
several  advantages  over  the  Deacon  meter.  If  all  unmetered 
services  in  a  given  section  be  cut  out  the  flow  into  that  section 
in  excess  of  the  meter  records  is  probably  leakage.  When 
leakage  is  in  sand  or  gravel  about  the  only  method  of  locating 
it  is  to  test  the  entire  piping  system  section  by  section,  either 
by  the  use  of  the  Deacon  meter  or  Pitometer  or  by  noting  the 
result  as  each  section  is  cut  out. 

Leakage  having  been  approximately  located,  the  pipe 
must  be  uncovered  and  the  leak  stopped.  If  it  is  found  to 
be  at  a  lead  joint,  calking  is  the  general  remedy.  If  at  the 
joint  between  a  corporation  cock  and  the  main,  it  may  some- 
times be  stopped  by  calking  the  threads  of  the  cock  against 
the  tap-holei;  but  it  is  better  to  disconnect  the  service-pipe, 
the  corporation  and  service  cocks  being  first  closed,  and 
screw  up  the  corporation  to  a  tighter  joint.  If  the  leakage 
be  at  a  valve,  the  packing  probably  needs  renewing  or  the 
bolts  tightening  up.  If  the  leak  be  caused  by  a  crack  in  the 
pipe,  the  damaged  pipe  should  be  broken  out  and  a  new  one 
put  in  its  place.  If  the  crack  be  near  one  end,  it  may  be  well 
to  cut  the  pipe  in  two  well  beyond  the  end  of  the  crack  and 
remove   only  the   broken   section.      For  cutting  pipes   in  the 


512 


yVA  TER-SUPPL  Y  ENGINEERING. 


trench  special  hand-machines  are  obtainable  (see  Fig.  93),  the 
use  of  chisel  and  hammer  for  this  purpose  being  an  exceedingly 
slow  method,  likely  to  result  in  failure  in  many  cases.  If  the 
crack  is  very  short,  or  the  leakage  be  through  a  blow-hole  in 
the  iron,  it  may  be  repaired  by  fastening  over  it  a  sleeve, 
made  in  two  halves  bolted  together  and  surrounding  the  pipe, 
lead   being  calked    between   the   pipe   and  each  end   of   the 


Fig.  93. — Pipe-cutting  Machine. 
sleeve.  The  use  of  a  sleeve  is  necessary  also  when  inserting 
a  new  section  of  large  pipe  to  replace  one  removed;  an 
alternative  method  when  a  whole  length  of  small  pipe  is 
replaced  being  to  melt  out  the  next  joint  each  way  from  the 
break,  raise  the  free  ends  of  the  two  end  pipes,  enter  the 
joints  at  each  end  of  the  new  pipe  while  all  are  suspended  in 
the  air,  and  let  all  three  drop  to  place  in  the  bottom  of,  the 
trench. 

A  joint  in  which  there  is  a  bead  on  the  spigot-pipe  cannot 
be  pulled  apart,  and  it  is  very  difificult  to  cut  the  lead  out. 
In  melting  it  out  a  hole  is  generally  dug  under  the  joint  and 
a  wood-fire  started  there.  In  some  cases,  especially  where 
there  is  water  in  the  trench,  this  is  impossible;  but  if  the  top 


PIPES  AND    CONDUITS.  51 3 

half  is  melted  out,  the  joint  can  generally  be  loosened  and 
pulled  apart.  A  better  plan  has  been  used  by  S.  W. 
Frescoln  and  is  described  by  him  in  Engineering  Ncxvs  of 
Sept,  9,  1897,  He  used  a  Wells  light  rigged  for  the 
purpose.  "  The  vertical  standpipe  was  taken  off,  and  by 
means  of  a  sufificient  length  of  flexible  rubber  hose  and 
fittings  two  burners  were  attached  to  the  cylinder  containing 
the  oil,  so  that  the  cylinder  could  be  placed  upon  the  pipe 
and  a  burner  be  operated  upon  two  joints  at  once.  The 
constant  services  of  one  man  were  required  to  operate  the 
burners  and  compress  the  air  in  the  oil-cylinder.  By  means 
of  suitable  tongs  and  rigging  made  from  ordinary  stiff  wire, 
the  flame  from  each  burner,  about  two  feet  long  ordinarily, 
under  a  blast  of  30  lbs.  was  directed  at  short  range  exactly 
against  the  lead  joint  at  the  top  of  the  bell.  .  .  .  The 
average  speed  made  was  from  8  to  10  joints  per  day  per  man, 
and  I  bbl.  of  oil  sufficed  for  about  12  joints." 

If  the  leak  is  found  to  be  at  the  valve  of  a  fire-hydrant,  it 
will  most  frequently  be  due  to  a  stick,  stone,  or  other  matter 
on  the  seat  which  prevents  the  valve  from  closing  entirely. 
This  matter  may  often  be  washed  out  by  simply  opening  the 
hydrant.  If  it  is  too  large  to  pass  the  nozzle,  remove  the 
cap  of  the  hydrant  and  let  the  water  come  directly  out  of  the 
top  of  the  barrel.  Stones  weighing  several  pounds  can  be 
thrown  out  in  this  way.  If  this  will  not  remove  the  obstruc- 
tion, a  boat-hook,  a  long  pair  of  tongs,  or  other  contrivance 
may  serve  the  purpose;  or  as  a  last  resort  it  may  be  necessary 
to  dig  around  the  hydrant,  remove  the  barrel,  and  thus  get 
at  the  obstruction. 

If  the  valve  of  the  fire-hydrant  is  cut  or  worn,  the  stem 
sprung,  thread  cut,  or  other  damage  done,  the  hydrant  or 
damaged  part  should  be  removed  for  repairs  and  immediately 
replaced  with  another. 

Breaks  of  considerable  magnitude  call  for  prompt  action 


514  ^^  TE/:-S  UPPL  Y  ENGINEERING. 

to  avert  great  damage  to  adjacent  property.  The  section  in 
which  the  break  occurs  should  be  at  once  cut  off  from  the 
systems  by  closing  the  necessary  valves,  and  the  ability  to 
immediately  locate  these  in  such  an  emergency  is  the  chief 
advantage  of  the  methodical  placing  of  valves  as  described  in 
Art.  94. 

Contraction  of  the  bore  of  a  pipe  generally  results  either 
from  deposits  of  inorganic  matter  in  the  pipe,  from  the 
growth  of  organic  matter  upon  its  inner  surface,  or  from 
tubercles.  The  first  should  be  prevented  to  a  great  extent 
by  purifying  the  water  before  admitting  it  to  the  pipes;  but 
a  deposit,  \vuen  once  in  them,  is  generally  removed  by  dis- 
charging water  in  as  great  volumes  as  possible  from  fire- 
hydrants  and  from  blow-offs  at  depressions  in  the  line;  the 
increased  velocity  which  results  stirring  up  the  sediment  and 
removing  it.  In  some  cases  the  deposit  is  so  compact  as  to 
require  other  methods  for  its  removal.  Scrapers  of  different 
designs  have  been  used  for  this  purpose.  Some  are  dragged 
through  by  a  rope,  which  has  first  been  passed  through  a 
section  of  pipe  by  making  an  opening  at  each  end  of  this  and 
floating  a  string  through  it.  The  scraper  generally  consists 
of  a  number  of  stiff  steel  arms  fastened  to  a  stout  centre,  the 
arms  being  designed  to  scrape  against  the  surface  of  the  pipe 
with  some  force.  While  dragging  the  scrapers,  water  must 
be  forced  through  the  pipe  to  wash  out  the  material  loosened 
up  and  prevent  its  choking  the  pipe  in  front  of  the  scraper. 
In  using  these  scrapers  it  has  not  been  found  practicable  to 
clean  more  than  1000  feet  of  pipe  at  a  time,  and  consequently 
breaks  in  the  pipe-line  must  be  made  at  intervals  of  not  more 
than  this  distance.  It  also  is  not  found  possible  to  drag  the 
scraper  around  a  bend  of  more  than  20°  or  30°,  and  a  break 
must  be  made  wherever  a  greater  angle  exists.  These  breaks 
must  of  course  all  be  repaired  by  new  pipe.  In  making  the 
breaks  the  cutting-machine  already  referred  to  will  be  found 


PIPES  AND    COXDUJTS. 


515 


PIPES   AND    CONDUITS.  517 

very  useful.  In  St.  John,  N.  B.,  special  hatch-boxes  are 
provided  to  permit  of  introducing  the  scraper  without  break- 
ing the  pipe. 

In  place  of  dragging  a  scraper  through  the  pipe  certain 
contrivances  have  been  employed  which  are  forced  through 
by  pressure  of  the  water  behind  them.  One  such  is  shown 
in  Fig.  94,  being  one  used  in  24-inch  pipe  in  St.  John,  N.  B., 
in  1898  by  Mr.  William  Murdoch,  and  described  by  him  in 
the  Journal  of. the  N.  E.  W.  W.  Ass'n  for  June  1899.  The 
force  used  to  operate  this  was  one  foreman,  one  mechanic, 
two  watchers,  six  assistants,  and  two  express  teams  and 
drivers.  "  The  watchers  walked  the  line  on  the  cleaner  being 
started,  and  had  no  difficulty  in  following  the  sound  outside 
the  city,  but  on  coming  inside  city  limits  the  noise  of  the 
traffic  drowned  the  sound  of  the  cleaner,  and  all  that  remained 
was  to  watch  and  wait  for  its  arrival  at  the  terminal  hatch- 
box.    .    .    .    The  cost  of  the  work  was  as  follows: 

Furnishing  and   placing  in    position    nine   24-inch 

and  four  12-inch  hatch  boxes $3,468.95 

Cost  of  one  24-inch  cleaner 40.00 

Total  cost  of  operating  cleaner 274.42 

**  The  operating  expenses  of  cleaning  the  main,  which 
measured  4.3  miles,  was  $63.84  per  mile." 

The  method  of  cleaning  distribution-pipes  in  Boston  is 
described  by  Mr.  Dexter  Brackett  in  the  same  number  of  the 
Journal  of  the  N.  E.  W.  W.  Ass'n,  as  follows:  "  As  many 
of  the  service  stop-cocks  project  into  the  pipes  from  \  io  '\ 
inch,  it  was  necessary  to  have  the  scraper  arranged  so  as  to 
pass  by  such  obstructions,  and  at  the  same  time  remove  the 
coating  of  tubercles.  The  machine,  which  was  very  success- 
fully used,  consisted  of  a  flexible  central  shaft  about  three 
and  one  half  feet  in  length,  composed  of  coiled  steel  springs 
connecting  small  castings,  to  which  were  hinged  two  sets  of 


5l8  WATER-SUPPLY  ENGINEERING. 

steel  scrapers,  arranged  radially  around  the  shaft  about 
twelve  inches  apart.  The  scrapers  were  kept  against  the  sides 
of  the  pipe  by  coiled  springs,  which  permitted  them  to  turn 
back  so  as  to  pass  taps  or  other  obstacles.  Back  of  the 
scrapers  were  two  rubber  pistons  placed  about  two  feet  apart 
so  as  to  insure  a  pressure  on  the  machine  when  passing  the 
branches.  ...  A  section  was  cut  out  of  the  pipe  long 
enough  to  receive  the  scraper,  which  was  then  inserted,  and 
the  joints  made  with  lead  in  the  ordinary  manner,  except 
that  clamp-sleeves  were  used  so  that  the  section  could  be 
again  easily  removed  and  the  scraper  inserted  if  desired.  A 
similar  piece  was  cut  from  the  pipe  at  the  other  end  of  the 
"Tiain  to  be  cleaned,  and  the  scraper  was  forced  through  the 
pipe  by  the  ordinary  water-pressure,  which  varied  from  30  to 
45  lbs. 

"  As  occupants  of  buildings  on  the  lines  of  the  pipes  were 
without  water  while  the  work  of  cleaning  was  in  progress,  and 
as  it  was  not  thought  advisable  to  pass  the  scraper  through 
the  valves,  the  pipes  were  cleaned  in  lengths  averaging  1000 
feet.  The  scraper  generally  passed  through  this  distance  in 
from  three  to  four  minutes,  or  about  as  fast  as  a  man  could 
walk.  In  a  few  instances  the  scraper  was  stopped  by 
obstructions  in  the  pipe,  the  one  causing  the  most  trouble 
being  lead  which  had  run  into  the  pipe  at  a  joint.  .  .  .  Some 
difficulty  was  experienced  from  the  stopping  of  service-pipes 
and  house-plumbing  by  rust  forced  into  the  pipes  by  the 
pressure  of  the  water  following  the  scraper,  but  this  difificulty 
could  be  generally  overcome  by  applying  a  force-pump  to 
the  house-plumbing  and  forcing  the  obstructions  back  into 
the  main. 

"  By  this  method  the  tubercles  were  removed  from  58,000 
feet  of  6-inch  pipe  at  a  cost  of  14  cents  per  foot,  and  from 
20,300  feet  of  12-inch  pipe  at  a  cost  of  20.6  cents  per  f9ot. 
These  prices  include   5   cents   per  foot  royalty  paid  for  the 


riFES  AND    CONDUITS.  5  IQ 

right  to  use  the  scraper.  .  .  .  The  discharging  capacity  of 
the  pipe  was  more  than  doubled  by  the  removal  of  the 
tubercles." 

Tubercles  are  the  obstructions  most  commonly  found  and 
removed  by  scrapers.  These  are  cone-shaped  projections  from 
■§■  to  I J  inches  in  height,  generally  hollow,  and  easily  broken  by 
the  finger-nail.  They  may  be  scattered  at  intervals  of  several 
inches  over  the  interior  of  the  pipe,  or  may  be  so  numerous 
as  to  form  a  continuous  rough  surface.  They  are  not  formed 
by  some  waters,  and  only  on  pipes  which  are  not  properly 
coated ;  although  in  pipes  which  are  apparently  well  coated 
they  may  form  where  minute  surfaces  of  iron  are  in  contact 
with  the  water.  In  cleaning  the  Sudbury  Aqueduct  (Boston) 
after  it  had  been  sixteen  years  in  use  about  two  cubic  yards 
of  tubercles  were  removed  from  22,619  square  feet  of  surface; 
and  from  some  pipes  a  cubic  yard  of  tubercles  has  been 
removed  for  each  1000  square  feet  of  surface. 

Mains  which  are  too  near  the  surface  sometimes  freeze, 
and  this  prevents  the  flow,  if  it  does  not  burst  the  pipe. 
Probably  only  the  smallest  mains — 4-  and  6-inch — ever  freeze 
shut  without  bursting.  Most  trouble  of  this  kind  is  in  con- 
nection with  the  service-pipes.  Several  methods  have  been 
employed  for  thawing  pipes.  Steam  is  forced  from  a  portable 
boiler  through  a  steam-hose  and  nozzle,  and  by  directing  the 
steam  against  the  ground  a  hole  is  bored  as  by  a  water-jet, 
the  nozzle  following  down,  until  the  pipe  is  reached  and 
thawed  by  the  steam.  Or  a  fire  is  built  on  the  surface  over 
the  pipe.  Or  the  pipe  is  uncovered  and  thawed  out  with  hot 
water.  Probably  the  best  method  yet  contrived  was  first 
used,  so  far  as  is  known,  in  the  early  part  of  1899,  originating 
with  members  of  the  faculty  of  the  University  of  Wisconsin. 
It  consists  of  heating  the  pipes  by  passing  electricity  through 
them,  the  current  being  conveniently  taken  from  the  electric- 
light  wires.      In  Ithaca,  N.  Y.,  a  4-inch  cast-iron  main  over 


520 


IV.-l  TEK-SUPPL  Y  ENGINEERING. 


lOO  feet  long  was  thawed  by  use  of  a  current  of  i6o  amperes 
in  5  hours  and  40  minutes,  the  pressure  in  a  2-inch  copper 
wire  being  9  volts.  At  Watertown,  Wis.,  320  feet  of  6  inch 
pipe  was  thawed  by  a  current  of  350  amperes  at  100  volts  in 
about  two  hours.  To  answer  numerous  inquiries  the  Uni- 
versity of  Wisconsin  issued  the  following  directions: 

"  The  current  which  is  required  for  satisfactorily  thawing 
service-pipes  up  to  i^  inches  in  diameter  is  from  200  to  300 
amperes.  The  source  of  current  should  have  a  pressure  of 
not  less  than  50  volts.  Where  electric-light  lines  carrying 
alternating  currents  are  available  a  transformer  or  transformers 
in  parallel  may  be  used  as  a  source  of  current.  It  is  very 
important  that  direct  connection  of  pipes  to  house-lines  be 
avoided  on  account  of  danger  of  fire,  in  which  the  house  is 
placed  by  such  connection.  Where  alternating  currents  are 
not  available  continuous-current  feeder-lines  may  be  used, 
but  these  should  be  entirely  separated  from  the  distributing 
network  of  conductors. 

"  The  accompanying  sketch  will  show  the  way  in  which 
the    appliances    should    be    connected    when    an    alternating 


Fig.  95. — Thawing  Pipes  by  Electricity. 

current  is  used  with  transformer.  The  secondary  leads  from 
the  transformer  should  be  quite  large,  such  as  No.  3  B.  &  S. 
gauge,  or  larger.      In  making  connection  to  the  pipes,  one  of 


PIPES   AND    CONDUITS.  521 

the  secondary  leads  should  be  taken  into  the  nouse  to  which 
the  frozen  service-pipe  leads,  and  contact  made  at  that  point 
by  some  form  of  metallic  clamp  or  by  simply  giving  the 
conductor  two  or  three  tight  twists  about  the  pipe  at  any 
point  where  the  pipe  is  exposed  or  at  a  faucet  in  the  house. 
The  other  secondary  lead  should  be  put  in  contact  with  the 
water  system  outside  of  the  house,  and  in  a  similar  manner. 
This  contact  may  be  made  at  a  hydrant  or  at  an  adjoining 
service-box,  or  pipes  in  a  neighboring  house.  When  there 
are  two  houses  near  together,  each  with  frozen  service-pipes, 
the  two  secondary  leads  may  be  connected  to  the  pipes  within 
these  houses  and  both  frozen  service-pipes  thawed  out  at 
once. 

"  While  the  thawing  process  is  going  on,  the  faucet 
should  be  open  in  the  house  to  which  the  service-pipe  leads. 
In  one  of  the  secondary  leads  should  be  inserted  a  water- 
resistance  which  consists,  for  convenience,  of  a  bucket  of 
wacer  containing  a  bowlful  of  salt,  and  two  sheet-iron  c 
copper  plates,  to  which  the  ends  of  the  severed  lead  are 
attached.  This  serves  to  control  the  current.  In  the  primary 
leads  from  the  electric-light  line  to  the  transformer  it  is  highly 
desirable  to  have  a  fuse  in  each  lead,  and  an  ampere-meter. 
When  all  connections  are  made,  the  plates  are  placed  in  the 
bucket  and  are  then  moved  towards  each  other  until  the 
ampere-meter  records  a  proper  current.  If  the  primary 
pressure  is  looo  volts  and  the  secondary  pressure  50  volts, 
the  current  should  ordinarily  approach  15  amperes.  If  the 
primary  pressure  is  2000  volts  and  the  secondary  pressure  50 
volts,  the  ampere-meter  reading  should  ordinarily  approach 
7.5  amperes. 

"  Water  ordinarily  begins  to  flow  in  a  time  not  much  less 
than  10  minutes  or  not  greater  than  one  hour.  If  the 
secondary  current  is  quite  close  to  300  amperes,  the  period 
seldom  exceeds  one-half  hour.      The  pipes  are  often  split  by 


522  IVA  TEH-SUPPLY  ENGINEERING. 

the  action  of  the  frozen  water,  and  these  at  once  begin  to 
leak  when  the  ice  is  thawed  away.  For  this  reason  it  is 
desirable  to  have  a  plumber  where  he  may  be  readily  called 
to  care  for  the  leaky  pipe. 

"  The  electric  current  when  properly  used  will  not  damage 
the  pipes.  It  is  desirable  to  watch  brass  and  iron  connections 
to  lead  or  iron  service-pipes,  as  they  sometimes  heat  on 
account  of  poor  contact.  If  such  heating  appears  to  be 
excessive,  the  current  may  be  reduced  with  a  resulting 
increase  in  the  duration  of  time  for  thawing. 

"  After  the  pipe  has  been  thawed  it  is  desirable  to  let  the 
water  run  continuously  for  a  considerable  time,  inasmuch  as 
the  ground  all  around  the  pipe  is  frozen  and  the  pipe  is  liable 
to  freeze  again  unless  water  circulates." 

Fire-hydrants  sometimes  freeze,  generally  because  of  a 
leak  in  the  valve.  They  can  be  thawed  by  the  use  of  steam 
from  a  portable  boiler;  but  a  more  convenient  plan  is  by  the 
use  of  hot  air  from  an  oil-stove,  which  is  led  to  the  inside  of 
the  hydrant  by  a  hose,  through  which  motion  of  the  air  is 
caused  by  use  of  a  small  hand-blower.  Fire  around  the 
hydrant,  burning  waste  inside  of  it,  and  similar  methods  are 
not  recommended,  as  their  use  is  liable  to  crack  the  cast  iron, 
cause  the  valve-stem  to  bend  out  of  line,  and  produce  other 
injury  to  the  hydrant. 

An  inspection  of  all  valves  and  curb-cocks  should  be  made 
occasionally  to  ascertain  whether  they  are  in  working  order, 
and  are  closed  or  open,  whichever  is  desired.  Circulation 
through  the  distribution  system  is  sometimes  interfered  with 
by  a  closed  valve,  which  thus  creates  two  dead-ends. 
Detroit,  Mich.,  has  a  special  gang  to  look  after  the  6000 
valves  in  the  system;  by  which,  in  1895,  671  valves  were 
found  to  be  out  of  order,  and  94  were  found  shut;  237  valve- 
boxes  or  manholes  were  repaired,  and  147  cleaned. 

Waste   of  water  can  be  prevented  only  by  the  greatest 


PIPES   AND    CONDUITS.  523 

vigilance  if  meters  be  not  used.  A  house-to-house  inspec- 
tion should  be  made  at  least  twice  a  year,  every  appliance 
for  using  water  be  examined,  and  the  service-pipes  be 
inspected  so  far  as  they  are  exposed  to  detect  the  existence 
of  any  unauthorized  fixtures.  The  most  common  locations 
of  leaks  and  waste  are  named  in  Art.  14.  Also  a  block-to- 
block  test  of  the  mains  should  be  made  between  i  and 
5  A.M.,  when  it  is  assumed  that  no  water  is  being  used,  and 
if  any  flow  be  found  (by  methods  described  in  the  first  part 
of  this  article),  its  outlet  and  cause  should  be  investigated. 
The  use  of  meters  is  preferable  to  inspection,  however,  being 
more  certain  in  its  results.  Each  meter  should  be  tested  for 
accuracy  before  being  set,  and  in  some  cities  each  meter  is 
tested  once  in  one  or  two  years,  and  whenever  its  accuracy  is 
impugned  by  a  complaining  citizen.  Sensitiveness  also  is 
desirable  in  a  meter,  that  it  may  register  small  wastes  as  well 
as  large.  If  a  large  number  of  meters  are  in  use,  a  mechanic 
should  be  employed  who  is  able  to  make  necessary  repairs 
upon  these;  and  he  will  also  find  additional  occupation  in 
connection  with  fire-hydrants,  valves,  curb-cocks,  etc. 
Repairs  to  meters  are  required  generally  because  of  freezing, 
of  stoppage  caused  by  a  stick  or  other  foreign  substance  in 
the  water,  of  breaking  of  the  diaphragm  or  piston  (unusual 
in  a  good  meter),  or  of  wear  in  the  recording  mechanism. 
One  or  two  designs  of  meters  are  now  provided  with  frost- 
bottoms,  which  are  claimed  to  prevent  damage  to  the  meter 
if  it  freezes.  In  most  meters  the  recording  mechanism  can 
be  removed  and  replaced  with  a  new  one  without  disturbing 
the  meter  or  its  connections.  The  maintenance  of  meters, 
including  reading  the  dials  quarterly,  should  not  cost  more 
than  $,40  to  $1.50  each  per  annum.  In  Fitchburg,  Mass., 
in  1898  maintenance  of  2177  meters  cost  an  average  of  65 
cents  each.  The  cost  of  keeping  in  repair  582  meters  in 
Reading,    Pa.,  during  the  year  of   1898-9  was  S62,  or    lof 


524  WATER-SUPPLY  ENGINEERING. 

cents  each.  In  1892  repairs  in  Waltham,  Mass.,  cost  13 
cents  per  meter;  in  Springfield,  Mass.,  13  cents  per  meter; 
in  Detroit,  Mich.,  12  cents,  and  in  Binghamton,  N.  Y.,  36 
cents.  The  life  of  a  good  meter  will  probably  average  about 
20  years. 

Art.  111.     Service  Connections  and  Extensions. 

The  connection  between  the  main  and  a  house  is  generally 
called  the  "  service  connection."  The  service-pipe  is  ordi- 
narily from  \  to  i^  inches  diameter,  f  or  f  being  a  common 
size  for  dwellings.  Galvanized  iron,  lead,  cement-lined,  tin- 
lined,  lead-lined,  and  black  iron  pipe  are  all  in  common  use. 
The  use  of  black  iron  should  be  prohibited  in  the  majority  of 
systems,  if  not  in  all,  since  it  is  subject  to  tuberculation  and 
rust,  which  decrease  the  capacity  of  the  pipe  and  often  close 
it  altogether.  Tin-lined  pipe  is  an  excellent  pipe  if  well 
made,  since  few  if  any  potable  waters  have  any  effect  upon 
tin.  Cement-lined  pipe  gives  good  service  under  the  same 
conditions.  But  if  the  cement  become  cracked  by  rough 
handling  or  freezing,  or  is  of  poor  quality,  it  flakes  off  and 
not  only  leaves  the  pipe  unprotected,  but  frequently  clogs  it 
or  the  meter  or  plumbing  fixtures.  Galvanizing  on  iron 
seems  to  be  less  subject  to  flaking  and  peeling  in  actual 
service  than  do  cement  and  tin  as  generally  applied,  is, 
cheaper,  and  is  in  much  more  common  use.  A  disadvantage 
of  all  linings  is  that  the  iron  is  exposed  at  joints  or  wherever 
the  pipe  has  been  cut.  Lead-lining  has  been  used  which  can 
be  hammered  and  pressed  around  exposed  edges  to  protect 
them,  but  this  pipe  is  rather  expensive.  The  chief  objection 
to  lead  pipe  is  its  low  tensile  strength,  its  cost,  and  the 
danger  of  the  metal  being  taken  up  by  the  water  and  poison- 
ing consumers  (see  Art.  6).  All  of  these  objections  are  real 
ones;  the  last,  however,  only  when  waters  with  certain 
characteristics  are  used. 


PIPES   AND    CONDUITS.  5^5 

The  service  connection  consists  of  a  "corporation  cock," 
which  is  a  stop-cock  attached  to  the  main  and  generally  made 
to  open  and  close  with  a  socket  wrench;  a  "goose-neck " 
formed  of  about  three  feet  of  lead  pipe  bent  to  the  shape  of 
an  inverted  U,  forming  a  flexible  connection  between  the 
service-pipe  and  the  cock  in  order  that  settlement  of  the 
former  may  not  break  the  latter  (this  is  sometimes  omitted — 
unwisely,  the  author  thinks);  a  length  of  pipe  leading  to  the 
curb,  where  a  "  curb-cock  "  or  valve  is  placed  and  provided 
with  a  valve-box,  permitting  the  water  to  be  turned  on  or  off 
by  use  of  a  suitable  key;  and  from  this  a  pipe  leading  to  the 
house-plumbing. 

The  corporation  cock  is  made  of  brass  throughout.  Those 
used  some  years  ago  were  tapering  and  were  driven  into,  a 
tapering  hole  in  the  main,  where  they  were  held  by  friction. 
In  a  few  places  these  are  still  used;  but  those  now  in 
common  use  are  screwed  into  the  main,  a  hole  having  been 
drilled  in  this  and  threaded.  When  the  main  is  empty  the 
operation  is  very  simple;  but  if  the  system  is  in  service  the 
necessity  for  cutting  off  a  section  from  use  by  closing  all 
valves  and  emptying  the  pipe  of  water  is  a  serious  objection. 
To  avoid  this,  several  machines  have  been  designed  which 
will  drill  and  thread  the  hole  in  the  main  and  insert  the  cock 
without  the  loss  of  more  than  a  quart  of  water,  and  without 
shutting  off  the  pressure.  Among  these  are  the  Mueller, 
Lennox,  Smith,  Hall,  and  other  tapping  machines.  The 
cock  is  closed  when  attached  to  the  pipe,  and  is  not  opened 
(except  for  an  instant  to  test  it)  until  the  service  connection 
is  completed. 

The  goose-neck  may  be  either  soldered  to  the  corporation 
cock,  a  "  wiped  joint  "  being  made,  or  expanded  into  a 
union  designed  for  this  purpose  and  screwed  to  the  corpora- 
tion cock.  If  no  goose-neck  is  used,  the  pipe  is  screwed 
directly  onto  the  end  of  the  corporation  cock. 


526  WATER-SUPPLY   ENGINEERING. 

The  curb-cock  is  somewhat  similar  to  the  corporation.  It 
is  turned  by  a  key,  and  is  provided  with  a  "curb-box" 
extending  above  it  to  the  surface,  by  which  it  is  made 
accessible.  The  curb-box  should  be  adjustable  in  length 
when  in  place  and  without  digging  around  it,  unless  to  be 
placed  in  a  concrete  or  other  permanent  sidewalk. 

It  is  desirable  to  make  the  whole  service  connection  in  a 
practically  straight  line,  as  it  can  then  be  cleared  of  stoppage 
in  many  cases  by  running  a  stiff  wire  through  it  from  the 
house-end  (the  corporation  cock  being  first  closed,  and  after- 
ward opened  and  closed  suddenly  and  for  an  instant  only). 

The  service  connection  as  far  as  and  including  the  curb- 
cock  is  generally  constructed  by  and  retained  as  the  property 
of  the  company  or  department,  in  order  that  the  consumer 
may  have  no  right  to  interfere  with  the  turning  off  or  on  of 
the  supply  at  the  curb-cock,  and  to  prevent  the  tapping  of 
the  mains  by  any  but  experienced  employes  of  the  company 
or  department. 

Extensions  from  the  end  of  a  main  or  from  a  branch- 
special  previously  inserted  for  this  purpose  are  made  in  a 
manner  similar  to  the  original  construction.  If  a  plug  has 
been  inserted  in  the  end  of  the  pipe  or  branch,  the  pressure 
must  be  cut  off  from  this  by  closing  the  necessary  gates,  the 
plug  be  broken  out,  and  the  water  which  flows  from  the 
mains  drained  or  pumped  away,  before  the  extension  can  be 
laid.  In  some  instances  where  an  extension  in  the  near 
future  was  probable  it  has  been  thought  desirable  to  build 
this  at  once  as  far  as  the  nearest  gate  and  leave  this  closed. 
The  extension  can  then  be  laid  at  any  time  without  interter- 
ing  with  the  service,  and  the  gate  opened  when  it  is 
completed. 

In  case  it  is  desired  to  lay  a  branch-line  from  a  point 
where  no  branch-special  was  inserted,  a  length  of  the  pipe 
may  be  cut  out  here  and  a  suitable  special  inserted.    Machines 


PIPES  AND    CONDUITS.  527 

have  been  designed,  however,  for  connecting  with  any  size 
of  main  branches  of  2  to  42  inches  diameter  under  pressure 
up  to  1000  lbs. ;  working  similarly  to  the  corporation-cock 
tapping-machines.  These  machines  are  somewhat  expensive, 
but  may  be  either  bought  or  rented. 


Art.  112.     Prevention  of  Deterioration. 

Mains  when  once  laid  are  subject  to  few  destructive 
influences  not  provided  against  by  a  proper  designing  and 
coating.  The  internal  pressure  is  resisted  by  the  tensile 
strength  and  thickness  of  the  iron  shell;  pressure  from  with- 
out is  seldom  if  ever  sufificient  to  injure  the  pipe  if  this  be 
given  the  depth  of  covering  specified  in  Art.  98,  except  that 
a  settlement  of  ground  under  the  pipe  or  away  from  one  side 
of  it  may  cause  a  break  in  the  line  (although  a  lead-jointed 
pipe-line  can  generally  be  distorted  for  several  inches  before 
breaking);  friction  of  the  flowing  water  has  little  if  any  effect 
upon  mains  or  conduits,  unless  the  velocity  be  greater  than 
is  ever  obtained  in  a  distribution  pipe-system,  and  if  it  be 
greater  in  any  conduit  than  the  maximum  given  in  Art.  53 
the  error  in  design  should  be  corrected.  This  can  be  accom- 
plished in  the  case  of  open  conduits  by  building  in  them  at 
intervals  low  weirs  with  either  overfalls  or  sluices  at  their 
lower  sides;  the  reduction  in  velocity  necessitating  an 
enlargement  of  the  conduit,  unless  the  diminished  flow  will 
still  be  ample. 

Chemical  action  frequently  takes  place  in  metal  conduits, 
as  previously  stated,  unless  these  be  properly  coated.  A 
good  coating  seems  to  be  permanent  and  require  no  renewal, 
no  instance  having  come  to  the  author's  notice  where  this 
has  been  attempted.  Moist  soil  outside  the  conduit,  as  well 
as   the   water  within,    causes  an    injurious   chemical   action, 


528  WATER-SUPPLY  ENGINEERING. 

which  not  only  corrodes  and  pits  the  surface  of  the  metal^ 
but  frequently  changes  its  entire  character;  iron  pipe  having^ 
been  found  which  could  be  cut  with  a  knife.  This  can  be 
prevented  only  during  construction,  and  the  maintenance 
department  can  but  substitute  for  weakened  pipe  other  which 
has  been  properly  protected. 

During  the  last  few  years  electrical  action  upon  iron  pipe 
has  become  a  matter  of  greater  concern  than  either  mechani- 
cal or  chemical;  not  so  much  because  its  effect  is  more 
serious  as  because  its  prevention  is  more  difficult.  There  is 
probably  some  electrolytic  action  taking  place  in  many  water- 
mains,  particularly  at  their  junction  with  branches  of  brass  or 
other  metal,  even  when  there  are  no  large  artificially  created 
currents  in  the  ground ;  but  the  greatest  danger  seems  to  exist 
where  there  are  wandering  currents  from  trolley-roads.  So 
great  has  the  danger  under  these  conditions  seemed  to  be 
that  several  cities  have  employed  experts  to  examine  and 
report  upon  the  electrolysis  taking  place  in  their  distribution 
systems;  among  these  being  Dayton,  Ohio,  Jersey  City, 
N.  J.,  Brooklyn,  N.  Y.,  and  others.  The  experts  employed 
in  1898  by  Dayton — Messrs.  H.  P.  Brown,  E.  E.  Brownell, 
and  J.  H.  Shaffer — state  that:  "  The  current  to  operate  the 
trolley-cars  leaves  the  dynamo  and  passes  through  the  trolley- 
wires  in  various  parts  of  the  city,  then  through  the  motor  of 
each  car  and  the  wheels  to  the  rails.  To  complete  the  circuit 
it  must  return  to  the  negative  pole  of  the  dynamos.  To 
reach  this  pole,  two  paths  are  open  to  it :  first,  by  the  rails 
and  feeder  wires  leading  from  the  rails  to  the  dynamo;  and 
second,  through  the  moist  earth  to  the  water-  or  gas-pipes 
below,  along  which  it  passes  until  within  lOOO  to  3000  feet 
of  the  power-house,  when  it  leaves  the  pipes,  again  passing 
through  the  moist  earth  to  the  rails.  A  circuit  of  electricity 
passing  through  a  conducting  fluid  like  water  decomposes  it, 
and   the   oxygen   and   acids,    if   any,    in   the   compound    are 


PIPES   AND    CONDUITS.  529 

delivered  at  the  positive  or  outgoing  pole,  while  the  hydrogen 
and  alkalis  are  delivered  at  the  negative  or  receiving  pole. 
The  oxygen  corrodes  the  metal  of  the  positive  plate,  while 
the  hydrogen  produces  no  chemical  effect  on  the  negative 
plate."  "  The  rate  of  electrolysis  depends  directly  upon  the 
electrical  condition  of  the  electrical  pressure  between  the 
positive  and  negative  plates  (the  pipes  and  rails).  This  rate 
is  increased  by  the  presence  of  any  acid  or  alkali  in  the  fluid 
(or  soil  in  contact  with  pipes  and  "rails).  A  slight  leakage 
from  the  gas-pipes,  or  a  small  amount  of  acid  from  the 
surface,  or  the  presence  of  an  alkali  in  the  soil  will  increase 
the  action,  and  the  current  itself,  by  carrying  the  metal  oxide 
into  the  ground-water,  reduces  the  resistance  of  the  solution, 
and  tends  constantly  to  cause  a  further  increase  of  action." 
The  effect  of  electrolytic  action  in  wrought  iron  is  three 
times,  and  in  lead  seven  times,  as  great  as  in  cast  iron;  hence 
service-pipes  are  especially  liable  to  injury  by  electrolysis. 

The  general  method  of  ascertaining  whether  electrolytic 
action  is  taking  place  in  a  certain  line  of  pipe  is  to  take 
voltmeter-readings  between  the  pipe  and  the  trolley-rails 
above  it.  (Electric  connection  with  the  pipe  may  be  made 
at  a  gate  or  a  fire-hydrant.)  Where  the  potential  of  the  pipe 
with  reference  to  the  rail  is  positive  there  is  a  probability  of 
such  action  existing;  \\  to  2  volts  being  sufificient  to  cause 
alarm  and  call  for  further  investigation.  The  remedy  lies  to 
a  large  extent  not  with  the  water  department  or  company, 
but  with  the  trolley-road,  and  this  is  generally  the  most 
troublesome  feature  of  the  difficulty.  Insulation  of  existing 
water-mains,  or  even  of  those  laid  for  the  first  time,  seems  to 
be  impracticable,  and  to  prevent  the  passage  of  return 
currents  through  them  it  is  necessary  to  provide  other  return 
circuits  offering  less  resistance  to  the  current,  or  to  increase 
the  resistance  offered  by  the  pipe.  Since  most  if  not  all  of 
the  injury  to  the  pipe  is  confined  to  the  point  or  points  at 


530  WATER-SUPPLY  ENGINEERING. 

which  the  current  leaves  it,  it  is  generally  possible  to  so 
connect  the  pipe  and  rails  at  this  point  as  to  permit  the 
return  of  the  current  without  injury  to  the  former.  To 
increase  the  resistance  to  the  current,  wooden  pipe  has  been 
substituted  for  iron  in  some  plants  (see  Art.  94) ;  and  it  has 
been  suggested  that  an  occasional  pipe  of  wood  or  other  poor 
conductor  interspersed  along  each  line  would  be  effective. 
Mr.  H.  P.  Brown,  in  a  paper  read  before  the  American 
Society  of  Municipal  Improvements  during  the  summer  of 
1899,  says:  "I  again  urge  the  importance  of  thorough  and 
frequent  electrical  inspections  of  the  water-pipes  and  friendly 
consultation  with  the  railway  managers  when  dangerous  con- 
ditions are  found  to  exist.  And  I  again  advise  the  insertion 
of  lengths  of  iron-banded  wooden  pipes  into  the  water-mains 
at  intervals,  so  as  to  make  the  mains  of  less  conductivity  than 
the  rails.  This,  with  good  bonding  [of  the  rails],  suitable 
and  properly  balanced  return  wires  from  rails  and  water- 
mains,  and  continued  electrical  tests,  will  prevent  any  serious 
trouble  from  electrolysis." 

The  maintenance  of  irrigation  conduits  and  distributaries, 
which  are  generally  upon  the  surface  even  when  closed, 
requires  constant  inspection  to  prevent  or  quickly  repair  any 
break  or  other  injury  due  to  floods,  land-slides,  or  boulders, 
or  maliciously  inflicted.  For  this  purpose  the  system  is 
ordinarily  divided  into  sections,  each  with  a  tool-house  and  a 
small  gang  of  men  to  patrol  the  canal  and  make  repairs,  after 
the  general  plan  adopted  on  railroads.  It  is  also  desirable  to 
have  a  telephone  system  extending  along  every  canal,  enabling 
any  section-station  or  the  main  office  to  be  reached  from  any 
point,  each  inspector  being  provided  with  the  necessary 
instruments  for  tapping  the  line.  In  each  section-house 
should  be  kept  the  tools  adapted  to  repairing  whatever  kind 
of    conduit    exists    on    its    section,    and    the    bulky   material 


PIPES  AND    CONDUITS.  531 

necessary  for  this — as  lumber,  clay  and  gravel,  wooden  staves, 
etc. — should  be  stored  at  intervals  along  the  line. 

Many  of  the  suggestions  made  in  Arts.  104  and  105 
relative  to  masonry  dams  and  earthen  embankments  are 
equally  applicable  to  canals  and  masonry  conduits. 


CHAPTER    XXI. 
CLERICAL   AND   COMMERCIAL. 

Art.  113.     Keeping  Records. 

A  water-works  department  should  so  record  and  file  all 
data  relative  to  every  part  of  its  construction  and  maintenance 
that  they  may  be  easily  and  quickly  referred  to  and  be  per- 
fectly intelligible;  and  the  information  so  recorded  should 
embody  a  complete  description  of  the  plant,  and  the  nature 
and  date  of  all  changes  and  repairs.  These  data  will  gen- 
erally be  recorded  in  the  form  of  maps,  written  descriptions, 
and  financial  statements.  It  will  be  convenient  to  index  each 
of  these,  and  to  use  a  common  system  of  indexing  for  all. 
Thus  D9  may  refer  to  a  certain  street  intersection,  and  under 
this  heading  be  filed  all  maps  of  piping  and  appurtenances, 
all  descriptions  of  repairs  and  maintenance  operations  con- 
ducted at  this  point,  and  all  expenses  and  receipts  connected 
therewith. 

An  excellent  plan  is  to  have  one  map  of  the  entire  city 
to  a  small  scale,  showing  all  pipe-lines  but  no  details  or 
appurtenances.  This  map  may  be  divided  into  squares  by 
lines  drawn  approximately  at  right  angles  and  through  the 
middle  of  each  third,  fourth,  or  fifth  block,  each  line  being 
continuous  across  the  entire  map.  Successive  strips  running 
East  and  West  may  then  be  given  the  letters  of  the  alphabet, 
and  those  running  North  and  South  be  numbered,  a  sufificient 

532 


CLERICAL    AND    COMMERCIAL.  533 

number  of  the  first  letters  and  smallest  numbers  being  omitted 
to  allow  for  future  extensions.  A  combination  of  letter  and 
number  would  then  designate  a  particular  square;  D9,  for 
instance,  indicating  that  square  common  to  the  East  and 
West  strip  called  D,  and  to  the  North  and  South  one  called  9. 
D9-10  would  indicate  a  point  on  the  line  separating  strips  9 
and  10.  Reference  to  this  general  map  would  then  show  at 
once  under  what  heading  to  look  for  data  concerning  a  given 
location. 

This  method  applies  chiefly  to  the  distribution  system. 
Data  concerning  each  pumping-station,  reservoir,  filter,  etc., 
should  be  filed  separately,  but  these  will  not  generally  be  so 
numerous  as  to  require  a  system  of  indexing. 

One  drawer  or  compartment  may  then  be  given  to  all 
maps  referring  to  strip  A,  another  to  B,  etc. ;.  one  being 
reserved  for  pumping-station  and  engine  details,  another  for 
reservoirs,  filters,  etc.  In  each  drawer  or  compartment  the 
maps  are  arranged  consecutively  according  to  the  number  of 
the  strip.  An  index  of  streets  may  be  prepared,  giving  the 
blocks  crossed  by  each  street  and  the  part  of  the  street  con- 
tained by  each  block.  If  this  arrangement  is  carefully  carried 
out,  the  finding  on  the  map  of  any  part  of  the  city  should  be 
the  work  of  but  a  minute  or  two.  An  excellent  method  of 
storing  the  maps  is  that  in  use  at  Detroit,  described  in 
Engineering  Record  for  February  12,  1898;  the  maps  being 
uniform  in  size  and  bound  in  sets  of  about  30,  each  set  being 
suspended  from  a  rod  in  a  cabinet  6  feet  high,  12  feet  wide, 
and  2\  feet  deep.  Each  bound  set  may  contain  the  maps  for 
one  strip  A,  B,  etc. 

The  records  should  give  the  size,  location,  depth,  and 
exact  arrangement  of  all  pipes,  specials,  valves,  hydrants, 
and  all  other  appurtenances  of  the  system ;  as  well  as  details 
concerning  any  gas  or  other  pipes,  sewers,  electric  conduits, 
or  other  underground  structures  of  which  data  are  obtained 


534  WATER-SUPPLY  ENGINEERING. 

from  other  departments  or  during  excavations  in  connection 
with  the  water-works  system. 

All  work  done  should  be  described  both  in  writing  and  by 
drawings,  with  accurate  dimensions,  recorded  on  the  spot  in 
the  engineer's  note-book,  and  the  information  on  each  page 
of  this  should  be  entered  on  the  detail  maps  and  check-marked 
when  so  entered,  and  in  the  index  of  streets  the  number  and 
page  of  note-book  should  be  entered  under  the  proper  street. 

If  meters  are  used,  a  record  of  these  should  be  kept  in  a 
separate  book,  the  record  of  each  meter  being  kept  separately 
(it  being  convenient  to  place  upon  each  page  the  record  of 
the  meter  having  alike  number):  the  date  of  its  purchase; 
result  and  date  of  any  tests  made  upon  it;  date  of  placing  it 
in  service;  that  of  any  repairs,  with  character  and  cost  of 
these.  The  monthly  or  quarterly  readings  may  be  entered 
in  this  book,  or  in  a  separate  book  devoted  to  accounts  with 
the  consumers. 

An  account  should  be  kept  of  each  pumping-station,  and 
of  each  pump  and  boiler  in  the  same;  showing  the  amount, 
kind,  and  cost  of  coal  used,  as  well  as  of  all  other  supplies; 
the  daily  pumpage  of  each  engine,  with  the  average  head 
pumped  against  and  the  steam-pressure;  the  days  of  service 
of  each  boiler;  describing  also  any  repairs  made,  with  their 
cost,  and  giving  the  names  of  engineers  and  firemen  on  duty 
each  day. 

Records  should  also  be  kept  of  reservoirs,  showing  the 
height  of  water  each  day,  giving  the  dates  and  circumstances 
of  any  pollution  or  unpleasant  taste;  together  with  the  daily 
evaporation,  temperature,  and  atmospheric  moisture,  and 
both  the  daily  rainfall  and  maximum  rate.  This  will  require 
an  evaporation-pan,  a  hygrometer,  a  maximum  and  minimum 
thermometer,  and  a  recording  rain-gauge. 

It  is  generally  good  policy  to  publish  a  summary  of  these 
data  annually  and  forward  it  to  water  departments  in  other 


CLERICAL   AXD    COMMERCIAL. 


535 


Date  of  Construction. 
By  whom  Owned. 
Source  ot  Supply. 
Mode  of  Supply. 

1.  Builders  of  Pumping  Machinery. 

C  a.   Kind. 

'l  b.  If  Coal,  what  Brand? 
_         .     .        i  c.  Average  Price  of  Coal 

2.  Description  l  (j^oss  Ton,  deliv- 

ofP"el     \  ^red. 

used.  ^_   Percentage  of  Ash. 

I  /.  Wood, Price  per  Cord. 

\^/.  Other  Fuel.  Price. 

3.  Coal  Consumed  for  the  Year,  lbs. 
Pounds  of  Wood  Consumed 


WATER-WORKS  STATISTICS  (1903). 
I.  General  and  Pumiing. 

6.  Total  Pumpape  for  the  Year,  gallons. 


t,a.  Amount  of  other  Fuel  used. 

5.  Total  Fuel  Consumed  for  the  Year,  lbs 

II.  Financial 

Receipts. 


7.  Averafcje  Static  Head  against  Pumps. 

8.  .■\v.  Dynamic  Head  against  Pumps,  feet, 

9.  No.  of  Gallons  Pumped  per  Lb.  of  Coal. 

10.  Duty  in  Ft.  Lbs.  per  100  lbs.  of  Coal,  no 

Deductions. 

11.  Cost   per   Million  Gallons  Pumped  into 

Reservoir,  Figured  on  Pumping-sta- 
tion  Expenses, 

12.  Cost  per   Million    Gallons    Raised    One 

Foot  High,  Figured  on  Pumping-sta- 
tion  E.xpenses. 

Cost  per  Million  Gallons  Pumped  into 
Reservoir,  Figured  on  Total  Mainte- 
nance. 

Cost  per  Million  Gallons  Raised  One 
Foot  High,  Figured  on  Total  Mainte- 
nance. 


13 


14 


Balance  Brought  Forward: 
(rt)  From  Ordinary(Maintenance)  Receipts. 
\b)  Prom   E-xtraordinary  Receipts  (Bonds, 

etc.). 
From  Water  Rates. 

A.  Fixture  Rates. 

B.  Meier  Rates. 

C.  Total  from  Consumers. 

D.  For  Hydrants. 

E.  For  Fountains. 

F.  For  Street  Watering. 

G.  For  Public  Buildings. 
H.  For  Miscellaneous  Uses. 
I      General  Appropriation. 

T.     Total  from  Municipal  Depts. 
"K.  From  Tax  Levy. 
L.    From  Bond  Issue. 
M.  From  other  Sources. 
N.  Total. 


Expenditures. 

Water-works  Maintenance: 

AA.  Operation  (Management  and  Repairs). 

BB.  Special. 

CC.  Total  Maintenance. 

DD.  Interest  on  Bonds. 

EE.  Payment  of  Bonds. 

FF.  Sinking  Fund.  ^ 

Water-works  Construction. 

GG.  Extension  of  Mains. 

HH.  Extension  of  Services. 

II.      Extension  of  Meters. 

JJ.      Special. 

KK.  Total  Construction. 

LL.    Unclassified  Expenses. 

MM.  Balance. 

(aa)  Ordinary, 
(bb)  Extraordinary. 

Total  Balance. 

N.  Total. 


O.  Net  Cost  of  Works  to  Date. 
P.  Bonded  Debt  at  Date. 


Disposition  0/ Bnlance. 

I        Q.  Value  of  Sinking  Fund  at  Date. 
I        R.  Average  Rate  01  Interest. 

III.  Consumption. 

6.  Percentage  of  Consumption  metered. 

7.  .Average  Daily  Consumption,  gallons. 
Gallons  per  D.iy: 

8.  Each  Inhabitant, 
g.  Each  Consumer. 
10.  Each  Tap. 


Estimated  Population  : 

1.  Total  at  Date. 

2.  On  Line  of  Pipe. 

3.  Supplied  at  Date. 

4.  Total  Gallons  Consumed  during  Year. 

5.  Quantity  Used  through  Meters,  gallons. 

IV.  Distribution — Main  Pipes. 
Hydrants: 

9.  Number  Added  (Public  and  Private). 
10.  Total  in  Use  (.Public  and  Private), 
feet.  Stop-gates: 

Number  Added. 


1.  Kind  of  Pipe. 

2.  Sizes  of  Distribution  Pipe,  inches. 

3.  Length  Extended  during  Year,  feet 

4.  Length  Discontinued  during  Year,  f 

5.  Total  Length  in  Use,  miles. 

6.  Cost  of  Repairs  per  Mile. 

7.  Number  of  Leaks  per  mile. 

8    Length  of  Pipe  less  than  4  in.  diam.,  miles. 


12.  Total  in  Use. 

13.  Small  Stop-gates  less  than  4  in.,  total. 

14.  Number  of  Blow-nflf  Gates. 

15.  Range  of  Pressure  at  Center  of  Town,  lbs. 


V.  Distribution— Service-pipes. 


Service- pipe: 

16.  Kind  of  Pipe. 

17.  Sizes  of  Pipe,  inches. 

iS    L-ngth  Extended  during  \  ear.  feet. 
19!  Length  Discontinued  during  Year,  ft. 

20.  Total  Length  in  Use,  miles. 
Service-taps: 

21.  Niimt^p''  Added. 

22.  Total  in  Use. 

23.  Average  Length  of  Service. 

34    Average  Cost  of  Service  for  the  \  ear. 


Meters: 

25.  Number  Added. 

26.  Now  in  Use. 

27.  Percentage  of  Services  Metered. 

2S.  Percentage  of   Receipts  from  Metered 
Water '(.ff -4-  C). 
Motors  and  Elevators: 
21).  Number  Added. 
:!o.  To  al  in  Use. 

31.  Number  of  Standpipes  for  Street-water- 
ing. 


536  WATER-SUPPLY  ENGINEERING. 

cities  which  will  do  the  same;  since  much  of  value  can  be 
learned  by  this  interchange,  and,  the  various  departments 
being  in  no  way  competitors,  there  can  be  no  objection  to  the 
publicity.  The  value  of  these  data  is  greatly  increased  if 
those  of  all  cities  be  analyzed  and  arranged  uniformly. 

Two  or  three  general  systems  have  been  suggested,  but 
probably  more  water  departments  follow  that  adopted  by  the 
N.  E.  W.  W.  Ass'n  than  any  other.  This  arrangement  of 
statistics  is  given  on  page  535. 


Art.  114.     Meters  and  Rates. 

The  desirability  of  preventing  waste  was  stated  in  Arts. 
14  and  16;  and  the  use  of  meters  for  this  purpose  has  been 
referred  to.  These  devices  have  been  in  general  use  for  a  few 
years  only,  but  there  are  few  if  any  cities  in  which  they  have 
been  introduced  whose  water-works  officials  and  citizens  are 
not  in  favor  of  their  use,  although  much  opposition  to  their 
original  introduction  is  generally  encountered.  It  is  better 
to  introduce  meters  at  the  very  first,  both  because  consider- 
able senseless  opposition  is  generally  raised  to  their  introduc- 
tion later,  and  to  prevent  the  consumers  from  acquiring  the 
habit  of  wasting  water,  which,  like  other  habits,  it  is  difficult 
to  overcome.  One  of  the  best  arguments  for  meeting  public 
opposition  is  the  proof — generally  obtainable — that  in  the 
majority  of  cases  where  meters  are  not  used  ten  to  twenty 
per  cent  of  the  consumers  do  most  of  the  wasting,  which  the 
other  eighty  or  ninety  per  cent  must  pay  for  (see  page  43); 
and  also  that  if  the  water  be  metered  a  less  sum  than  the 
average  rates  which  are  being  or  would  otherwise  be  charged 
need  be  paid  by  any  but  recklessly  wasteful  consumers. 
Where  there  are  no  legal  obstructions,  it  is  generally  desirable 
to  set  as  a  minimum  amount  which  will  be  charged  for,  one 


CLERICAL   AND    COMMERCIAL.  537 

sufficient  to  fully  meet  all  requirements  of  health  and  clean- 
liness. 

There  are  a  number  of  excellent  meters  on  the  market, — 
and  several  worthless  ones.  No  cheap  meter  has  yet  been 
designed  which  is  also  good ;  and  the  hard  service  combined 
with  accuracy  required  would  seem  to  make  this  impossible. 
Delicacy — the  registering  of  small  quantities — is,  in  the 
author's  opinion,  more  important  than  extreme  accuracy; 
since  a  leak  or  other  constant  flow  at  a  low  rate  is  most  often 
the  cause  of  waste;  while  the  actual  charge  for  water  does 
not  warrant  incurring  extra  expense  to  insure  the  accuracy  of 
the  bill  within  only  a  few  gallons.  It  is  generally  considered 
advisable  that  a  meter  under-register  rather  than  over- 
register,  since  one  consumer's  complaint  found  justifiable  will 
more  than  outbalance,  in  the  popular  mind,  a  dozen  false 
claims  of  overcharging. 

For  ordinary  domestic  service  a  f-inch  meter  is  amply 
large.  For  large  hotels,  factories,  railroads,  and  other  large 
consumers,  4-  or  even  8-inch  meters  may  be  necessary.  The 
price  increases  rapidly  with  the  size.  For  service-pipes  of 
8-inch  diameter  or  above,  a  Venturi  meter  can  be  used  to 
advantage,  but  for  smaller  services  its  cost  is  excessive,  and  it 
is  not  so  sensitive  as  is  a  good  rotary  or  disk  meter. 

There  is  of  necessity  a  certain  amount  of  head  lost  in 
each  meter,  required  to  work  the  measuring  and  registering 
mechanism.  Meters  are  obtainable  which  consume  no  more 
than  I  to  5  lbs.  in  ordinary  service.  Four-  to  eight-inch  fac- 
tory meters  have  been  found  to  cause  a  loss  of  i.i  to  9.3  lbs. 
for  a  discharge  of  250  gals,  per  minute,  and  up  to  40  lbs.  for 
500  gals,  per  minute  (see  Journal  N.  E.  W.  W.  Ass'n,  De- 
cember 1897),  although  the  loss  during  a  flow  of  500  gals, 
has,  with  certain  makes  of  meters,  been  found  to  be  as  low  as 
4  lbs.  in  a  4-inch  and  0.7  lb.  in  an  8-inch  meter.  Of  fourteen 
f-    and    |-inch  meters  of    different    patterns   tested   by   Mr. 


538  WATER-SUPPLY   ENGINEERING. 

J.  W.  Hill  in  1898,  the  head  lost  varied  from  0.50  lb.  with  a 
discharge  of  about  170  gals,  per  hour  to  26.68  lbs.  with  a  dis- 
charge of  865  gals,  per  hour  (see  Trans.  Am.  Soc.  C.  E.,  vol. 
XLI.  page  326). 

Under  any  but  exceptional  circumstances  a  well-made 
meter  should  give  good  service  for  many  years.  The  con- 
sumption of  a  family  will  average  about  10,000  cubic  feet  per 
year.  Six  meters  tested  by  Mr.  J.  Waldo  Smith  in  1894-5 
registered  from  71 1,000  to  1,644,000  cubic  feet  each,  and  the 
four  of  these  which  had  passed  the  most  water  were  still  in 
running  order;  giving  a  life  of  71  to  164  years  of  average  use. 
The  meter  may  of  course  be  damaged  by  a  stick  or  stone  or 
may  be  stopped  by  tubercles  or  other  matter  collecting  in  it ; 
but  this  is  due  to  a  faulty  condition  of  the  pipe  or  water 
which  should  be  remedied ;  and  large  matters  may  be  kept 
out  of  the  meter  by  placing  a  screen  at  its  inlet.  While  the 
accuracy,  sensitiveness,  loss  of  head,  and  accessibility  for 
repair  of  any  meter  can  readily  be  ascertained  in  a  few 
minutes,  the  durability  cannot  readily  be  tested,  but  can  be 
judged  from  the  mechanical  perfection  of  the  various  parts 
and  the  hardness,  toughness,  and  non-corrosiveness  of  the 
materials  employed.  Meters  are  in  some  cases  owned  by  the 
company  or  department,  in  others  by  the  consumer;  the 
latter  is  occasionally  required  to  deposit  a  sum  sufificient  to 
cover  any  damage  to  the  meter  caused  by  him,  or  is  charged 
a  rental  for  its  use.  Their  use  is  compulsory  in  some  cities, 
optional  in  others.  Probably  the  majority  of  cities  begin  by 
metering  the  largest  service-pipes,  although  some  have  found 
the  greatest  waste  to  occur  from  plumbing  in  cheap  houses. 

The  services  rendered  by  a  water-supply  system  may  be 
considered  under  the  two  general  heads  of  public  and  private, 
and  returns  from  each  of  these  may  be  justly  demanded. 
The  public  services  include  fire-protection,  street-sprinkling, 
sewer-flushing,  public  fountains,  and  other  similar  purposes 


CLERICAL   AND    COMMERCIAL.  539 

for  which  the  municipality  as  such  makes  use  of  water.  The 
private  services  include  all  those  for  which  water  is  taken 
from  house-service  connections,  to  be  used  upon  private 
premises,  whether  in  the  house  or  the  barn,  in  sprinkling 
lawns,  running  elevators,  etc.  A  determination  of  the  rates 
will  generally  be  based  upon  the  value  of  the  services 
rendered  to  the  consumers,  and  the  cost  to  the  company  or 
department;  the  latter  of  which  is  much  the  more  readily 
estimated  and  forms  the  principal  basis  of  charges  in  most 
cases. 

Fire-protection  requires  the  furnishing  of  little  additional 
water,  but  proper  provision  for  it  increases  by  at  least  one 
third  the  original  cost  of  most  plants.  The  supply  for 
sprinkling  streets,  flushing  sewers,  and  other  public  purposes 
probably  amounts  to  between  5  and  25  per  cent  of  the  total 
consumption  in  most  cities.  It  would,  upon  this  basis,  seem 
just  to  obtain  from  the  public  treasury  {a)  33^  of  the  interest 
upon  the  cost  of  construction  and  of  the  annual  contribution 
to  the  sinking  fund,  and  {b)  10  or  15  per  cent  of  the  running 
expenses;  the  remainder  {c)  to  be  paid  by  private  consumers. 
The  payment  of  {b)  and  (r)  is  frequently  based  upon  actual 
measurement,  where  this  is  possible. 

Where  the  water-works  are  owned  by  a  private  company 
the  revenue  from  fire-protection  generally  takes  the  form  of 
hydrant  rental;  that  from  other  public  services  is  in  some 
cases  determined  by  meter,  in  others  a  lump  sum  is  paid,  but 
in  most  this  is  included  in  the  hydrant  rental,  or  is  given  as 
a  return  for  the  franchise.  When  owned  by  the  city  the 
water-works  are  usually  under  the  control  of  a  separate 
department,  and  all  revenue  is  received  and  disbursements 
made  by  this.  In  many  cities  the  department  receives  no 
revenue  for  public  services,  but  instead  asks  for  and  some- 
times receives  annual  appropriations  from  the  public  treasury. 
The  praiseworthy  practice  is  becoming  more  general,   how- 


540 


WATER-SUPPLY  ENGINEERING. 


ever,  of  making  the  department  self-supporting,  and  of  paying 
into  its  treasury  revenues  {ii)  and  {U),  as  a  private  company 
would  be  paid.  The  advantages  of  this  plan  are  appreciated 
by  every  water-works  superintendent  who  has  annually 
struggled  with  successive  councils  for  his  appropriation,  and 
has  conducted  his  department  with  embarrassing  uncertainty 
as  to  the  amount  he  will  receive. 

The  hydrant  "rentals"  received  by  different  water  com- 
panies vary  between  very  wide  limits,  as  is  shown  by  the 
following  table.  This  variation  is  partly  due  to  differences 
in  the  cost  of  the  plants,  but  more  to  the  shrewdness  of  the 
company  or  carelessness  of  the  city  officers  in  preparing  the 
franchise.  The  majority  of  rates  given  in  the  table  are  seen 
to  lie  between  $15  and  $50. 


HYDRANT    RENTALS    IN    THE    UNITED    STATES    IN    iJ 
(From  the  "  Manual  of  American  Water-works.") 


Hydrant 
Rate. 

North- 
western. 

South- 
western. 

Pacific. 

Total  for 
Western. 

Total 
Eastern. 

Total 
UnitedStates 

Free 

%     5 
10 

I 

I 

15 
2 
2 

17 
2 
2 

26 

43 

16                       tS 

15 

29 
22 
24 

33 
26 

44 

27 

60 

8 

24 

29 
26 

4 

6 

2 

4 

6 

5 
2 

9 

5 

29 

3 

18 

7 
8 

16 

20 

10 

3 

36 

I 

I 

I 

I 

25 
30 
35 
40 

45 
50 
55 
60 

65 
70 

75 
80 

I 
2 

I 

2 

2 

12 

30 
38 
28 

I 
I 

3 

I 

13 
3 
9 
2 

4 
12 

5 
3 

4 
I 

4 

53 
32 
89 

8 
4 
4 
4 
4 
6 

3 
15 

I 

I 

42 

7 

s 

24 

40 

II 
I 

85 

90 

100 

120 

4 
5 

41 

18 

3 
I 

125 
150 
160 

I 

I 

I 

CLERICAL    AND    COMMERCIAL.  54^ 

The  geatest  differences  and  difficulties  are  found  in  fixing 
rates  for  private  consumption.  In  probably  a  majority  of 
cases  a  rate  is  fixed  for  each  kitchen  faucet,  water-closet,  and 
other  appliances  for  using  water.  There  seems  to  be  no 
uniformity  in  the  rates  for  each  of  the  various  fixtures,  either 
actual  or  relative.  Of  thirty  cities  having  a  population  of 
80,000  or  over  whose  rates  were  studied  by  Mr.  August 
Hermann  in  1899,  the  cost  for  0  six-room  house  occupied  by 
one  family  on  an  18-  or  20-foot  lot,  having  a  yard  hydrant, 
kitchen  sink,  stationary  wash-stand,  bath  with  hot  and  cold 
water,  water-closet,  and  two-tray  laundry,  varied  from  $3.70 
per  annum  in  Detroit  to  $31.75  in  New  Orleans,  the  average 
being  1 15.42.  For  a  twelve-room  house  having,  besides  the 
above,  two  stationary  wash-stands,  one  bath  with  hot  and 
cold  water,  and  two  water-closets,  the  rates  varied  from  Si 3 
in  Baltimore  to  $52.25  in  New  Orleans,  averaging  $28.84. 
In  some  cities  the  rates  are  given  for  seventy-five  to  one 
hundred  items,  in  others  for  not  more  than  twelve  or  fifteen. 
These  items  include  fixtures  as  such,  purposes  for  which  the 
water  is  used,  character  of  building,  size  of  building  or  lot, 
and  nature  of  business  conducted  therein.  Brooklyn  and 
Albany,  N.  Y.,  charge  for  vacant  lots,  the  latter  10  cents  per 
annum  per  front  foot,  the  former  from  10  cents  per  running 
foot  for  lots  assessed  at  $100  or  under,  up  to  20  cents  for 
those  assessed  at  $2000  or  over. 

Meter  rates  are  in  some  cases  graduated,  in  others 
""  straight  "  or  "flat."  Straight  rates  range  from  5  cents  to 
$1  or  more  per  looo  gals.,  probably  averaging  about  20  or  25 
cents.  Graduated  rates  are  based  upon  the  amount  of  con- 
sumption, large  consumers  obtaining  low  rates.  There  are 
two  general  methods:  basing  the  rate  for  each  month, 
quarter,  half-year,  or  year  (the  period  for  which  payments 
are  made)  upon  the  total  consumption  for  that  time;  or 
charging  a  certain  amount  for  the  first  unit  quantity  of  con- 


542 


IV A  TER-SUPPL  V   ENGINEERING. 


sumption  during  that  time,  and  a  decreasing  amount  for  each 
additional  unit  quantity.  By  the  first  method  the  charge 
might  be  50  cents  a  thousand  gallons  for  20,000  gals,  or  less^ 
30  cents  for  more  than  20,000  and  less  than  40,000  gals.,  etc.^ 
In  this  case,  if  a  consumer  found  that  his  meter  registered 
between  19,000  and  20,000  gals,  at  the  end  of  the  quarter,  it 
would  be  to  his  advantage  to  waste  sufficient  water  to  bring 
this  above  20,000  and  obtain  the  lower  rate.  To  prevent 
this  several  cities  have  adopted  the  second  plan.  At  Madi- 
son, Wis.,  the  rates  are  as  follows: 


For  the  first    5,000  cu.  ft.  in  six  months, 

"       "    next  15,000  "     "     "  " 
"       "       "      10,000  "     "     "     " 

"       "       "     30,000  "     "     "  " 

"       "       "     30,000  "     "    "  " 

Over  90,000  "     "    "  " 


20  cts.  per  100  cu.  ft. 
10    " 

5    " 

3    " 

2  " 

3  " 


The  rates  at  Reading,  Penn.,  are: 


First        1,000  gallons  or  less  per  month, 

50    cts.  p 

er  1000  gallo 

Next       2,000 

22      " 

"          2,000 

18     "       ' 

"          5,000         ' 

14     "       ' 

"        10,000         ' 

8     "      ' 

"        10,000         ' 

6     "       ' 

"        20,000 

5     "       ' 

"        50,000         ' 

4i  "       ' 

100,000 

4     "       ' 

"      300,000 

3|  "       • 

"      500,000 

3i  "       ' 

"  2,000,000         ' 

3     "      ' 

Over  3,000,000         ' 

2f   "       ' 

In  many  if  not  a  majority  of  cases  a  minimum  charge  is 
made  of  from  $1  to  $5  to  cover  reading  the  meter  and  clerical 
work,  with  interest  on  the  cost  of  the  service  connection. 

(Sec  also  Tables  74  and  75,  Appendix  A.) 


clerical  and  commercial.  543 

Art.  115.     Financial. 

A  city  or  irrigation  water-supply  system  which  is  owned 
and  operated  by  a  private  company  will  be  conducted  upon 
ordinary  business  principles;  but  to  apply  these  it  is  necessary 
to  know  beforehand  what  will  be  the  cost  of  construction  and 
of  maintenance,  and  what  the  life  of  the  plant.  In  the  case 
of  municipal  ownership  there  is  generallj''  the  additional 
problem  of  paying  for  the  construction.  Few  cities  could  pay 
cash  for  this  from  their  treasury,  nor  is  it  considered  desirable 
to  compel  the  present  inhabitants  to  furnish  a  water  system 
free  of  debt  to  their  descendants  or  successors;  but  these 
should  pay  as  much  per  annum  for  the  service  rendered  as 
does  the  present  generation. 

An  ideal  plan  would  be  to  issue  such  bonds  and  make 
such  annual  payments  toward  a  sinking  fund  that  when  the 
piping  system,  for  instance,  shall  need  renewing  the  bonds 
by  which  it  was  built  will  just  mature  and  be  exactly  met  by 
the  sinking  fund ;  and  that  the  same  be  true  of  the  reservoirs, 
pumping-plant,  and  other  parts  of  the  system.  Extensions 
would  be  paid  for  in  the  same  way;  and  repairs  on  a  given 
section  would  be  paid  for  out  of  the  sinking  fund  connected 
with  that  section.  This  plan,  if  carried  out  in  all  its  details, 
would  be  unnecessarily  complicated,  but  it  can  be  followed 
in  a  general  way;  the  plant,  for  instance,  being  divided  into 
the  reservoirs  and  permanent  head-works,  the  piping  system, 
the  pumping-plant,  and  the  filtration-plant;  any  smaller  items 
being  combined  with  that  class  which  is  thought  to  have  a 
similar  length  of  life.  Extensions  could  be  paid  for  by  the 
proceeds  from  a  bond  issue  made  once  every  five  years  or  so. 
Service  connections  and  maintenance  would  be  paid  out  of 
the  annual  receipts;  the  former  generally  being  charged 
against  each  property  when  it  is  connected  with  the  main. 
The  rates  must  be  so  fixed  that  the  receipts  will  be  sufficient 


544  WATER-SUPPLY  ENGINEERING. 

to  meet  the  maintenance  expenses  and  interest  on  the  bonds, 
and  make  the  annual  payments  into  the  sinking  fund. 

The  cost  of  constructing  the  various  parts  of  the  plant 
has  already  been  considered.  The  life  of  a  plant  can  seldom 
be  estimated  with  any  exactness.  A  well-built  reservoir 
should  have  a  life  terminated  only  by  the  insufficiency  of  its 
capacity.  A  pipe-line  of  cast  iron  also  should,  if  well  coated, 
be  serviceable  until  its  capacity  is  exceeded  by  the  consump- 
tion. The  experts  appointed  to  appraise  the  value  of  the 
property  of  the  Los  Angeles  City  Water  Company  considered 
the  life  of  the  cast-iron  pipe  to  be  from  50  to  80  years;  of 
the  riveted-iron  and  steel  pipe  to  be  15  to  25  years;  of 
■wrought-iron  standard-screw  pipe  to  be  from  17  to  30  years. 
An  internal  depreciation  also,  due  to  tuberculation,  was 
allowed  for.  The  life  of  pumps  depends  upon  their  original 
character  and  the  care  taken  to  maintain  them.  A  well- 
designed  and  constructed  pump  should  give  good  service  and 
efficiency  for  at  least  forty  years.  The  boilers  will  not 
ordinarily  last  so  long.  Probably  thirty  years  would  be  a  fair 
estimate  of  the  average  length  of  life  of  a  pumping-plant. 
The  life  of  filter-plants  has  already  been  considered  in 
Arts.  TT,  78  and  108. 

The  cost  of  maintenance  of  filter-plants  has  been  treated 
of  in  Art.  108;  that  of  conducting  a  pumping-station  in 
Art.  107.  The  cost  of  repairs  in  the  distribution  system  in 
Fitchburg,  Mass.,  in  1896  was  $5.32  per  mile  of  pipe,  and  in 
Taunton  the  cost  of  repairs  and  maintenance  in  1893  was 
$20.55,  in  1895,  $25.33;  and  in  1896,  $29.85.  The  total 
maintenance  in  Taunton  during  the  same  years  cost  $39.37, 
$49.04,  and  $49.82  ;  and  the  total  expenses  of  the  plant  were 
$119.57,  $163.55,  and  $166.55.  At  Newton,  Mass.,  the 
maintenance  in  1897  cost  $27.55,  ^^^  interest  on  bonds 
$140.67,  per  million  gallons.  Maintenance  in  the  two  latter 
cases  was  the  total  maintenance  of  the  plant.      Maintenance 


CLERICAL   AND    COMMERCIAL.  545 

of  the  distribution  system  will  ordinarily  cost  $15  to  $35  per 
mile  per  annum,  including  pipes,  valves,  fire-hydrants,  etc., 
but  not  service  connections.  If  there  be  an  unusual  number 
of  leaks  and  breaks  in  the  line,  these  may  increase  the  cost  to 
$100  or  more.  Service  connections  will  generally  cost  about 
$5  to  $7  each  up  to  and  including  the  curb-cock,  and  20  to 
35  cents  per  foot  from  here  to  the  house;  but  the  cost  of 
these  is  generally  paid  by  the  consumer  at  the  time  the 
connection  is  made,  although  the  company  or  department 
retains  all  rights  of  ownership  of  that  part  up  to  and  including 
the  curb-cock.  Under  the  head  of  maintenance  must  be 
included  all  costs  of  administration,  ofifice  force,  collectors, 
etc. 

Water-rents  are  collected  monthly  in  some  cities,  quarterly 
in  others,  and  in  still  others  half-yearly.  Probably  the  plan 
of  quarterly  collections  is  the  one  most  generally  adopted. 
In  most  cities  the  failure  of  any  consumer  to  make  payment 
within  a  given  time — say  two  weeks — of  presentation  of  the 
bill  results  in  the  water  being  shut  off  from  his  premises  until 
all  indebtedness  is  settled,  including  a  small  additional  sum 
for  the  trouble  of  closing  and  opening  the  curb-cock.  In 
some  instances  a  discount  of  5  to  20  per  cent  is  allowed  for 
immediate  payments;  in  others  interest  is  charged  after  about 
ten  days  from  the  time  when  payment  is  due. 

A  few  water  companies  and  departments  have  made  it  a 
rule  that  excessive  waste,  if  continued  after  a  warning,  be 
stopped  by  cutting  off  the  supply  from  the  premises  of  the 
offender.  Probably  a  better  plan,  seeming  less  arbitrary  and 
being  more  remunerative,  is  to  introduce  meters  on  such 
services  (if  they  are  not  already  in  general  use),  and  follow 
the  customary  rule  of  shutting  off  the  supply  until  payment 
has  been  made  for  all  the  water  passing  the  meter. 

Since  the  receipts  during  the  first  year  or  two  after  the 
construction  of  the   plant  are  likely  to  be  small,   while  the 


54^  WATER-SUPPLY  ENGINEERING. 

expenses  of  maintenance  will  then  be  as  great  as,  if  not 
greater  than,  after  all  weak  points  have  been  discovered  and 
repaired,  and  experience  has  pointed  out  many  methods  of 
economizing,  it  may  be  desirable  to  begin  the  regular  pay- 
ments into  the  sinking  fund  only  after  the  first  or  second 
year,  as  otherwise  the  high  rates  necessarily  charged  would 
discourage  rather  than  encourage  the  general  use  of  the 
system. 


APPENDIX   A. 


Table  No.  73. 


DEATH-RATES    FROM    TYPHOID    FEVER    PER     100,000    OF     POPULATION 

PER    ANNUM. 

(See  page  24.) 


Class. 


B^ 


City. 


Munich. 
Vienna. 


The  Hague. 

Berlin 

Rotterdam  . 

Breslau 

Hamburg. . 

Zurich 

Amsterdam. 

London 

Edinburgh . 
Warsaw. . . . 
Lawrence . . 


Frankfurt  a.  M. 
Copeuhagen. . . 

Dresden 

Brussels 

Venice 

Dayton 

Lincoln 

Paris 


Rochester. . . . 

Brooklyn 

New  York, . . . 
Manchester... 

Newark 

Boston 

Glasgow 

New  Haven. . 
Fall  River.  .  . . 
Cambridge. . . 
Sydney,  N.  S. 
Worcester. . . . 
Baltimore.  . . . 
Liverpool 


W. 


f     Montreal. 
I  ,  Quebec, 
E'l  '  Trenton, 
I  I  Omaha. . 
M  Toledo-  . 


Death-rate  during 


8 
9 

3 
9 
6 

15 
28 
10 

19 

16 

19 

21 

123 


9 

9 

26 

44 
20 

37 
30 

33 
21 
21 

31 
107 

43 
26 
28 
62 
34 


17 

57 
24 


19 
36 
42 


isgi     1003 


12 
10 

4 
12 

23 

8 
II 

15 
18 

25 
"5 

5 
8 
8 
41 
33 
32 
24 
20 

36 
21 
22 

39 
72 

33 
31 
20 


21 

34 
25 


25 
20 
26 


6 
15 
34 

9 
15 
II 

13 

30 
95 

8 
7 
5 
23 
30 
44 
53 
28 

52 
18 
14 

25 
79 
25 
18 

29 
38 
20 
20 

57 
42 
25 


22 
13 
37 


1893    1894   1895 


15 

7 

2 

9 
5 
10 
18 
8 
16 
16 
14 
19 
69 

4 
9 
4- 

27 
26 
64 

58 
25 

39 

18 

20. 

25 

31 

26 

20 

31 
20 
21 
19 
33 
47 
53 

20 
50 
28 

14 

28 


2-5 

5 

3-4 

4 

4.8 

6.1 

6 

7 

8.5 
15 
15 
18 


7 

6.7 

8.2 

14 
18 
20 
26 
29 

12 

15.6 

17 

18 

21 

23 

24 

26 

29 

29 

29 

32 

49 

58 

20 
22 
23 

25 
26 


31 


38 


24 
16 

17 

2T 
32 

34 
33 
IS 

25 
28 


23 
18 
16 
12 

35 


547 


548 


APPENDIX. 


Table  No.  73. — Continued. 

DEATH-RATES     FROM     TYPHOID    FEVER    PER    100,000    OF    POPULATION 

PER    ANNUM. 


Class. 


F^ 


G^ 


H^ 


City. 


New  Orleans. 

St.  Louis 

Paterson 

Minneapolis. . 


Hamilton,  Ont. 

Toronto 

Milwaukee. . . . 

Detroit 

Cleveland 

Chicago 

Buflfalo 


Genoa 

Rome 

Denver 

San  Francisco.. . . 
Wilmington,  Del. 

Syracuse 

Reading 

Providence 

Hartford 

Scranton 


Richmond 

Philadelphia* 

Lowell 

Grand  Rapids 

Columbus 

Cincinnati 

Albany 

Troy 

Jersey  City. ....... 

Atlanta 

Pittsburg 

Camden. . . .; 

Louisville 

Washington 

Alexandria,  Egypt. 
Cairo,  Egypt 


Death-rate  during 


1890 


20 

34 

29 

41 

30 
80 

33 
18 
66 
83 
44 


35 
217 

45 
89 

33 
54 
29 
60 

57 


64 
82 
50 
74 
67 
60 
42 
97 
149 

131 
141 


23 
30 
21 
45 

20 
90 

33 

13 

52 

160 

56 


36 


34 
53 
49 
48 

47 
73 
54 

60 

64 

96 

65 

51 

62 

108 

80 

102 

119 

100 

56 

81 

86 

348 

233 


21 

37 
18 
36 

30 
40 

31 

51 

54 

103 

38 

23 
26 

53 
32 
43 
34 
45 
36 
82 
93 

68 

34 
90 

74 
46 
40 
50 
44 
73 
87 
100 

63 
72 
72 
77 
163 


1893 


15 


1894 


28 


1895 


103 

40 

31 
37 

60 

45 

10 

20 

40 

20 

37 

26 

61 

26 

47 

27 

42 

31 

37 

62 

35 

13 

34 

30 

57 

35 

34 

37 

69 

41 

31 

45 

38 

47 

34 

49 

50 

51 

62 

82 

53 

31 

41 

32 

62 

60 

94 

45 

45 

48 

43 

50 

59 

52 

57 

54 

68 

56 

66 

43 

III 

56 

60 

67 

84 

72 

72 

72 

79 

100 

155 

135 

41 
19 

21 

38 


25 
24 
36 
32 
28 


30 
32 
38 

51 

31 

58 

105 

27 

39 
28 

51 

36 

165 
51 
73 

77 
69 

77 
69 


•  During  an  epidemic  in  Philadelphia  in  the  early  part  of  1899,  3424  cases  of  typhoid  fever 
and  380  deaths  were  recorded  in  :o  weeks,  there  being  419  new  cases  and  39  deaths  in  the  one 
week  ending  March  nth. 


APPENDIX. 

Table  No.  74. 


549 


POPULATION,  WATER-CONSUMPTION,  RECEIPTS,  AND  NUMBER  OF 
TAPS  AND  METERS  IN  USE  IN  I900  IN  FORTY  CITIES  OF  THE 
UNITED    STATES.* 


Cities. 


Philadelphia.  Pa... 

St.  Louis,  Mo 

Cleveland,  Ohio  .  . . 

Buffalo,  N.  Y 

Washington,  D.  C. 

Detroit,  Mich 

Newark,  N.  J 

Jersey  City,  N.  J. . . 

St.  Paul.  Minn 

Columbus,  Ohio.. . . 
Worcester.  Mass. . . 
Fall  River,  Mass. . . 

Lowell,  Mass 

Portland,  Ore 

Atlanta,  Ga 

Hartford.  Conn.  . .  . 

Reading,  Pa 

Camden,  N.  J 

Lynn,  Mass 

Lawrence,  Mass.... 
New  Bedford,  Mass 
Springfield,  Mass.  . 

Troy,  N.  Y 

Salt  Lake  City 

Duluth,  Minn 

Harrisburg,  Pa. . . . 

Yonkcrs,  N.  Y 

Saginaw,  Mich 

Brockton,  Mass. . . . 
Pawtucket,  R.  I. . . 
Springfield,  Ohio... 

Tacoma,  Wash 

Springfield,  111 

York,  Pa 

Schenectady,  N.  Y. 
Fitchburg,  Mass. . . 

Taunton,  Mass 

La  Crosse.  Wis 

Woonsocket,  R.  I.  . 
Pueblo,  Col 


Popu 

ation 

Average 

Consump- 

Annual 

Number 

tion  per 

Receipts 

of  Taps. 

of  Meters 

By  Census 

Supplied. 

Consumer 

per 

in  Use. 

of  1900. 

Consumer 

1,293,700 

1,254,000 

229 

$2.43 

250,000 

1.275 

575,200 

400,000 

159 

3-71 

65.688 

4.133 

381,800 

420,000 

159 

1.82 

63,632 

3,143 

352,400 

400,000 

233 

1.62 

64.638 

1,049 

287.700 

270,000 

185 

1.30 

45,000 

1,200 

285,700 

306.055 

146 

1-52 

55.340 

5.555 

246,070 

255,000 

94 

2.71 

33.500 

7.342 

206,433 

200,000 

160 

4.19 

25.000 

500 

163,065 

125,000 

67 

2.77 

17.093 

4.812 

125.560 

100,000 

230 

1.65 

14,608 

4.960 

118,421 

113,000 

70 

2.32 

13,292 

12,536 

104,863 

104,500 

36 

1. 61 

6.943 

6.544 

94,969 

94,000 

85 

2.15 

10,634 

5.586 

90,426 

90,000 

200 

3.18 

12,447 

509 

89,872 

65,000 

84 

2.06 

9.275 

8,500 

79,850 

80,000 

106 

3.12 

9,351 

2,550 

78,961 

77,900 

92 

2.07 

15.885 

636 

75.935 

50,000 

280 

3.22 

14,000 

197 

68,513 

73,000 

64 

2.88 

12,577 

2,500 

62,559 

57.200 

56 

1. 81 

5,926 

4,386 

62,442 

55.000 

"5 

3- 30 

9,280 

1,429 

62.059 

48.200 

113 

5.06 

9.764 

3,122 

60,651 

58,000 

183 

1.80 

7,500 

314 

53.531 

55.000 

218 

1.82 

12,000 

145 

52,969 

15,000 

273 

8.87 

2,795 

1,261 

50.167 

57,000 

144 

2.03 

12,000 

4,278 

47.931 

45,000 

81 

3-29 

4,968 

4,852 

42,345 

28,000 

268 

1. 61 

3.500 

300 

40,063 

35.000 

32 

2.20 

5.275 

4,300 

39.231 

80,000 

82 

2.41 

8.293 

6,369 

38,253 

33,000 

91 

1.30 

4,200 

200 

37.714 

40,000 

TOO 

2-37 

4.500 

500 

34.159 

18,000 

222 

3-72 

3.000 

230 

33,708 

36,oco 

79 

2.58 

8.300 

275 

31,682 

27,000 

222 

2.78 

7,000 

20 

31.531 

25,000 

120 

2.74 

4.437 

2,427 

31,036 

26,100 

62 

•  2.32 

4.502 

1,832 

28,895 

29,000 

193 

1. 14 

3.300 

40 

28,204 

32,000 

29 

2.28 

2.347 

2,136 

28,157 

15,000 

267 

4.17 

3,400 

30 

•  Compiled  from  Reports  of  Geo.  I.  Bailey,  from  Engineering  News  of  April  18,  1901. 


550 


APPENDIX. 


Table    No.    75. 


POPULATION,  WATER-CONSUMPTION,  AND  RECEIPTS  FOR  WATER, 
SUMMARIZED  AND  AVERAGED  IN  ACCORDANCE  WITH  PERCENT- 
AGE OF  TAPS  METERED  (136  CITIES  OF  THE  UNITED  STATEs).* 


Percent- 

01 

4; 

U 

0 
w 
u 

a 

3 

2 

Popula- 
tion.t 

Consumption, 
(Gallons  per  Day). 

tit 

U 

0 

V 

a 

3 
2 

Popula- 
tion.! 

Receipts. 

age  of 

Taps 

Metered. 

Total. 

Av. 
per 
Con- 
sumer. 

Total. 

Av. 

per 
Con- 
sumer. 

0  to    10 
10  to    25 
«S  to    50 
50  to  100 

71 
18 
2a 
23 

12,713,866 
1.657,454 
1.686,63s 
1,600,333 

1,947.378,000 
182,991,000 
175,632,000 
109,616,000 

"S3 
no 

104 
62 

S3 
12 

17 
20 

102 

11,802,154 
1,108,142 
1.448,633 
I.4SS.443 

$26,432,316 
2,491.719 
3.»SS.M9 
3,253,606 

$2.24 

2.35 
2.35 

2.24 

Totals    & 
Averages 

134 

17,658,288 

2,415,617,000 

137 

15,814  371 

S3S.43».790 

$».24 

*  From  Reports  of  George  I.  Bailey.     From  Engineiring  News  of  April  18,  1891. 
t  The  table  is  based  on  the  population  supplied,  where  separately  reported  ;  otherwise  on 
the  total  population  by  the  census  of  1900. 


APPENDIX   B. 


HYDRAULICS. 


JETS. 

Within  the  past  few  years  the  author  has  made  experi- 
ments in  the  Hydrauhc  Laboratory  of  Lafayette  College 
which  have  shown  conclusively  that  a  jet,  when  discharged 
through  a  standard  orifice  in  a  vertical  plate,  has  no  "  con- 
tracted vein,"  if  by  this  term  is  meant  the  point  of  smallest 
cross-section  beyond  which  the  jet  again  enlarges.  For  about 
one  and  a  half  diameters  from  the  orifice  the  jet  decreases  in  size 
quite  rapidly  ;  beyond  this  point  it  continues  to  decrease,  but 
less  rapidly,  and  assumes  an  oval  section,  the  major  axis  being 
horizontal.      At  any  point  more  than  two  diameters  from  the 

0 
orifice  the  area  of  cross-section   equals  very  exactly  — "" , 


APPENDIX.  551 

in  which  Q  is  the  quantity  of  water  discharged,  and  h  is  the 
total  head  from  the  surface  of  the  water  to  the  centre  of  cross- 
section  at  the  point  in  question. 

CURVES. 

An  extended  series  of  experiments  have  recently  been 
made  by  Gardner  S.  Williams,  C.  W.  Hubbell,  and  G,  H. 
Fenkell  upon  the  head  lost  in  curves,  by  which  it  is  apparently 
demonstrated  that  a  sharp  curve  causes  less  lost  head  than 
does  one  of  a  long  radius ;  consequently  that  the  formulas 
ordinarily  used  are  incorrect.  It  would  appear  from  these  that 
the  lost  head  per  foot  of  curve  is  much  greater  in  the  sharp 
than  in  the  flat  curve,  but  that  the  greater  length  of  the  latter 
causes  a  greater  total  loss  of  head  ;  except  that  when  the 
radius  is  less  than  2  to  2\  diameters  the  lost  head  increases 
inversely  as  the  radius,  and  consequently  that  the  least 
resistance  is  offered  by  a  curved  pipe  laid  to  a  radius  about  2\ 
times  its  diameter.  This  assumes  that  in  each  case  the  same 
angle  of  deflection  is  attained  within  a  length  of  pipe  of  80 
diameters.  The  experiments  do  not  warrant  any  more  full  or 
definite  statement  than  the  above.  For  full  description  of 
these  experiments,  see  Transactions  American  Society  of  Civil 
Engineers  for  December,  1901. 

VALVES. 

Recently  experiments  have  been  made]  by  the  author  and 
his  students  on  the  head  lost  in  4-inch  valves,  in  which  more 
delicate  gauges  were  used  for  measuring  this  head  than  have 
ever  been  used  in  similar  experiments.  It  is  therefore 
thought  that  the  head  lost  in  an  open  or  nearly  open  valve  has 
been  determined  more  accurately  in  these  than  in  other  experi- 
ments. The  following  table  gives  the  results  of  these  experi- 
ments, as  well  as  of  those  by  Weisbach,  Kuichling,  and  Smith. 


552 


APPENDIX, 

Table  No.  76. 
head  lost  in  valves. 


Height  of  Opening 
Diameter  ot  Valve 


Weisbacirs  (smaller  ihan  2")  ...    . 
FolwelTs  (4"  wedge-valve) 

■'  (4"  parallel  face  valve) . 

Kuichling's  (24"  valve) 

Smith's  (30"  valve) 


j/8 

1/4 

3/8 

1/2 

5/8 

3/4 

7/8 

97.8 

17.0 

5-52 

2.06 

0.81 

0.26 

0.07 

72.3 

1(5.8 

6.ig 

2.58 

1 .22 

0  St 

0  20 

104.0 

20.3 

2.72 

0.66 

22.7 

8.6 

1 .00 

0.26 

98.6 

18.6 

7.68 

3-52 

1.64 

°-55 

O.IO 

0.0 
0.0 
0.0 
0.0 
0.0 


NoTB. — The  total  lost  head  in  each  case  is  diminished  by  that  for  a  wide-open  valve. 
For  approximate  rules  for  allowing  for  curves  etc.,  see  Appendix  D. 


APPENDIX    C. 

FILTRATION    DATA. 

Until  recently  there  has  been  little  definite  information 
concerning  the  efficiency  and  cost  of  sand  filters  in  this 
country.  Data  relative  to  three  plants  are  now  available, 
and  are  herewith  presented. 


Table    No.  77. 

DATA     CONCERNING     SAND     FILTRATION    OF     WATER     IN     AMERICA. 


Date. 


o 

O  O 

a;  e 

u  u 


Between 
Scrapings. 


,*- 

O  oi 

tr,   C 

C  0 

O  — 

■-  a 

Q 

S 

Cost  per  Annum. 


•5« 
>  S 

o  o 

a  c 


LAWRENCE,   MASS.,   FILTERS.       2-3  ACRES. 


97-5 

8  0 

98.6 

4.8 

98.9 

31 

98.6 

1.9 

99-5 

1.6 

r32 

109 

1 29 

90 

1 26 

80 

98.6 

1-4 

•  20 

74 

25 

85 

ig 

f^i 

[22 

85 

(  20 

7' 

99.1 

3  3 

i" 

78 

(•3 

49 

Total. 


lu  o  — 


$2 
81350 
1950 

S50 
$1460 
840 

$.320 
1 180 
2200 

$1000 
2120 
1950 

$2780 
2350 
2330 

$450 
490 
850 

$7.80 
8.10 
9.00 

1930 

300 

1660 

1600 

3480 

7.0 

8.00 

2060 

1270 

1470 

1450 

2300 

500 

7.70 

3130 

1250 

1410 

1510 

2330 

720 

7.70 

$80.85 
89  32 

100.99 


96.61 


90.32 

93-31 


APPENDIX. 


553 


Table    No.  77. — Continued. 

DATA    CONCERNING    SAND    FILTRATION    OF    WATER    IN    AMERICA. 


Date. 


£.5 
a. 


^ 

Between 

> 

Scrapings. 

C  T3  g 

O  u 

■^  o  o" 

en  a 

C  0 

S.   O-w 

o  = 

SE^^ 

.-o 

a 

Q 

2 

Cost  per  Annum. 


Son 
i^  olt/2 


I— 1  II 


Total. 


ALBANY,    N.    Y.,    COVERED    FILTER.       5-6    AREAS. 
MOUNT    VERNON,     N.    Y.,    FILTER.       I.I    ACRES. 


189s 
1896 
1897 

1 

1 

983     1 

8 

2.01 

20.70 

4* 
24 

73 
43 

21 

37 
34 

1.99 
2.46 

25.24 

876 

'336" 

322 

"33 

35-5' 

1898 

32 

40 
12 

^1 

77 
23 

1266 

339 

342 

289 

29 

3.30 

47.29 

26 

26 

12 

46 

25 

26 

26 

45 

50 

•5 

16 

28 

3' 

37 

24 

6s 

46 

35 

21 

72 

41 

19 

38 

1899 

22 

•9 
22 

42 
45 

46 

1464 

5^6 

419 

59° 

4.46 

67.39 

22 

26 

»9 

«3 

39 

47 

7 

25 

14 

48 

29 

25 

52 

3« 

31 

16 

63 

34 

23 

18 

46 

30 

22 

16 

27 

48 
40 

51 

1900 

24 
II 

30 
20 

47 
20 

57 
38 

202A 

512 

'45 

68 

4.05 

57-39 

24 

34 

46 

65 

34 

48 

67 

82 

13 

27 

25 

46 

'5 

33 

28 

56 

53 

102 

I90I 

15 
23 

44 
50 

24 
44 

73 
76 

♦Filter  put   into   service   in   September   18 
X  Average  of  all  beds. 


t  1.5   of  this  imported  cases    of    feve,'. 


APPENDIX    D. 

TABLES    FOR    PRACTICAL   USE. 

Table  No.  78. 
areas  of  pipe  sections. 


Diameter  of 
Pipe,  Inches. 

Area  of  Pipe, 
Square  Feet. 

Diameter  of 
Pipe,  Inches. 

Area  of  Pipe, 
Square  Feel. 

Diameter  of 
Pipe,  Inches. 

Area  of  Pipe, 
Square  Feet. 

4 
6 

8 

10 

O.0S727 
0.19635 
0.34907 
0-5454I 

12 

14 
16 

18 

0.78540 
I. 06901 
1.39626 
I. 76715 

20 
22 

24 
26 

2.18166 
2.63981 

3-I4159 
3.68700 

1,000,000  gallons  per  day  —  92,84  cu.  ft.  per  min.;   =  1.55  cu.  ft.  per  sec. 


Table   No.   79. 

VELOCITY     OF     FLOW     IN     PIPES.       FEET     PER     SECOND. 


Gallons 

Size  of  Pipe.     Inches. 

per  Day. 

4 

6 

8 

10 

12 

14 

16 

18 

20 

22 

24 

xo 

100 

1,000 

10,000 

100,000 

1, 000,000 

2,000,000 

3,cx)o,ooo 

4,000,000 

.00018 
.0018 
.018 
.177 
1.77 
17-73 

.00008 
.0008 
.0079 
.079 
0.79 
7.88 
15.76 
23-64 

.000044 
.00044 
.0044 
.044 
•443 
4-43 
8.86 
13.29 
17.72 
22.15 

.000028 
. 00028 
.ooaS 
.0284 
.2837 

2.837 

5.674 

8.511 
11.348 
14   18 

.0020 
.0197 
.197 

1.97 

3-94 

5.91 

7.88 

9.85 
19.70 

.0014 
.0145 
.145 
1.447 
2.894 
4-341 
5-788 
7-235 
14-47 

.0011 

.OIIX 

.1108 
1.108 
2.216 
3-324 
4.452 
5-540 
11. oS 

.0009 
.0088 
.0S76 
.876 
1.752 
2.628 
3-504 
4.380 
8.76 

2 
2 

3 

0007 

0071 

0709 

709 

418 

127 

836 

545 

.cx>o6 

.0059 

.0586 

.586 

1. 172 

1.758 

2   344 

2.930 

5.86 

.0005 

.0049 

.0492 

■492 

.984 

1.476 

1.968 

2.460 

4.92 

24.6 

lO.OOO.CXXD 
50,000,000 

The  friction  factor /for  iron  pipe  20  or  more  years  old  may  be  taken 

_       -04 
64/W^ 


For  most  purposes  it  is  sufficiently  accurate  to  assume  that — 
Head   Lost  in  an  open  valve  (above  that  in  an  equal  length  of  straight 

pipe)  equals  that  in  5  ft.  of  straight  pipe. 
Head  Lost    in    an    ordinary    cast-iron    90°    bend  equals    that  in   10    ft.   of 

straight  pipe. 
Head  Lost  in  an  ordinary  tee  equals  that  in  3  ft.  of  straight  pipe. 
Head   Lost  in  an  ordinary  cross  equals  that  in  10  ft.  of  straight  pipe. 

554 


APPENDIX   E. 

Quality  and  Analysis. 

Test  for  Hardness. — Use  a  standard  soap  solution  com- 
posed of  either  (i)  lo  grammes  of  new  Castile  soap  dissolved 
in  \  litre  of  alcohol  and  |  litre  of  water;  or  (2)  28  grammes  of 
olive-oil,  10  c.c.  sodium  hydrate  solution  of  36°  B.  and  10  c.c. 
of  alcohol  of  90%  to  95%,  saponified  on  water-bath  and  agi- 
tated with  800  to  900  c.c.  of  alcohol  of  60%;  either  solution 
to  be  filtered  into  a  bottle,  the  latter  to  be  increased  to  i  litre 
by  addition  of  60%  alcohol.  The  solution  must  be  standard- 
ized as  follows  :  Dissolve  i  gramme  of  pure  Ca  CO,  in  a  little 
HCl,  neutralize  with  slight  excess  of  NH,OH  and  dilute  to  i 
litre  ;  place  10  c.c.  of  this  and  90  c.c.  of  pure  water  in  an  8- 
oz.  glass-stoppered  bottle,  add  soap  solution  \  c.c.  at  a  time, 
shaking  well  after  each  addition,  until  a  lather  forms  which 
remains  for  5  minutes.  Add  the  soap  solution  in  the  same  way 
to  100  c.c.  of  pure  water  until  lather  forms;  the  difference  be- 
tween the  amounts  of  soap  solution  required  in  the  two  cases, 
divided  into  10,  gives  the  number  of  m.g.  of  calcium  carbonate 
corresponding  to  i  c.c.  of  soap  solution.  (This  ratio  changes 
with  the  age  of  the  solution.)  Ten  times  this  ratio  times  the 
number  of  c.c.  of  soap  solution  required  to  make  a  lather  in  100 
c.c.  of  the  water  to  be  tested  gives  the  hardness  expressed  in 
parts  of  Ca  CO,  per  million  of  water.  In  the  Clark  scale  a 
"degree"  corresponds  to  one  part  in  70,000  of  water.  (This 
method  is  not  accurate  for  very  hard  water.)  For  tests  in  the 
field  a  bottle  holding  about  200  c.c.  and  marked  at  the  100  c.c. 
line,  and  a  medicine-dropper  or  fountain-pen  filler  marked  into 
^  c.c.  lengths  are  convenient. 

555 


556 


APPENDIX. 


Test  for  Turbidity. — The  United  States  Geological  Survey- 
test  of  1902,  prepared  by  Hazcn  and  Whipple,  is  described  as 
follows.  (Water  Supply  and  Irrigation,  paper  No.  ^(b)}  Take 
a  stick  of  wood  about  5  feet  long  and  f  inch  square,  more  or 
less,  and  insert  a  platinum  wire  at  a  point  about  i  inch  from 
the  end,  so  that  the  wire  will  be  at  right  angles  to  the  stick 
and  project  at  least  i  inch.  The  wire  should  be  0.04  inch  or 
I  m.m.  in  diameter  ;  the  stick  is  then  graduated,  the  lines  for 
the  various  turbidities  being  at  distances  from  the  wire  shown 
in  the  accompanying  table. 


Turbidity. 

Depth  of  Wire. 

Turbidity. 

Depth  of  Wire. 

Turbidity. 

Depth  of  Wire. 

m.m. 

m.m. 

m.m 

7 

1.095 

30 

296 

140 

76.0 

8 

971 

35 

257 

150 

72.0 

9 

873 

40 

228 

160 

68.7 

10 

794 

45 

205 

180 

62.4 

II 

729 

50 

187 

200 

57-4 

12 

674 

55 

171 

250 

49.1 

13 

627 

60 

158 

300 

43-2 

14 

587 

65 

147 

350 

38.8 

15 

551 

70 

138 

400 

35-4 

16 

520 

75 

130 

500 

30.9 

17 

493 

80 

122 

600 

27.7 

18 

468 

85 

116 

800 

23-4 

iq 

446 

90 

no 

1,000 

20.9 

20 

426 

95 

105 

1,500 

17. 1 

22 

391 

100 

100 

2,000 

14.8 

24 

361 

no 

93 

3.000 

12. 1 

26 

336 

120 

86 

28 

314 

130 

81 

Observations  of  turbidity  are  taken  b)-  putting  this  stick  into 
the  water  under  examination  as  far  as  the  wire  can  be  seen ; 
the  turbidity  is  then  read  from  the  scale.  This  is  most  con- 
veniently accomplished  by  having  a  second  or  smaller  stick 
placed  in  front  of  the  first,  the  end  of  which  is  brought  to  the 
water-line  when  the  wire  can  just  be  seen.  Upon  removing 
the  two  together  the  position  of  the  smaller  stick  on  the  scale 
gives  turbidity.     Observations  are  to  be  taken  in  all  cases  in 


APPENDIX.  557 

open  air,  as  too  high  results  arc  obtained  under  a  roof,  even 
with  very  good  hght  ;  and  they  should  preferably  be  taken  in 
the  middle  of  the  day  and  not  in  direct  sunlight.  In  case  the 
sun  is  shining  the  observer  can  stand  so  that  his  shadow  covers 
the  water  immediately  about  the  stick  and  wire.  The  obser- 
vations arc  taken  with  the  eye  of  the  observer  at  a  wire  ring 
placed  on  the  stick,  1.2  meters  from  the  wire,  although  some 
variation  in  this  does  not  materially  influence  the  result.  The 
wire  should  be  kept  bright  and  clean.  In  case  it  is  lost  a 
clean  bright  pin  can  be  used  until  another  wire  can  be  obtained. 
When  the  surface  of  the  water  in  the  stream  is  agitated  by  cur- 
rents, waves,  etc.,  or  in  case  the  depth  is  not  sufficient  to  give 
the  required  immersion,  or  if  for  any  reason  observations  can- 
not be  well  taken  from  the  bank,  a  pail  or  tub  may  be  filled 
with  water  and  the  turbidity  observations  taken  in  it.  In  many 
cases  this  procedure  is  preferable  to  measurement  in  a  stream, 
but  the  observation  must  be  taken  immediately  upon  filling  the 
vessel.  The  diameter  of  the  vessel  should  be  equal  to  at  least 
twice  the  depth  at  which  the  wire  is  immersed,  as  otherwise 
the  results  of  the  reading  \\\\\  be  affected. 

Taste  and  Odor,  Organisms  givmg. — "  Almost  all  surface 
waters  have  some  odor.  Many  times  it  is  too  faint  to  be  noticed 
b)'  the  ordinary  consumer,  though  it  can  be  detected  by  one 
whose  sense  of  smell  is  carefully  trained.  On  the  other  hand, 
the  water  in  a  pond  may  have  so  strong  an  odor  that  it  is  offen- 
sive several  hundred  feet  away.  Between  these  tw^o  extremes 
one  meets  with  odors  that  vary  in  intensity  and  in  character, 
and  that  are  often  the  source  of  much  annoyance  and  com- 
plaint." ("  The  Microscopy  of  Drinking-water,"  Whipple.) 
Odor  and  taste  are  closely  related,  and  most  waters  having  an 
odor  have,  or  appear  to  have,  a  similar  taste.  Odor  and  taste 
are  caused  b}-  living  organisms,  by  other  organic  matter,  and 
by  the  decomposition  of  these.  The  first  are  of  quite  common 
occurrence,  are  generally  offensive  and  affect  large  bodies  ol 


558  APPENDIX. 

water.  In  most  or  all  cases  the  odors  are  produced  by  com- 
pounds analogous  to  essential  oils.  These  odors  and  the  or- 
ganisms producing  them  are  not  found  in  fresh  ground  water 
nor  at  all  abundantly  in  streams,  but  in  ponds,  reservoirs,  and 
lakes.  When  these  are  large  and  deep  organisms  which  grow 
attached  to  the  shores  produce  little  or  no  effect  on  the  water  ; 
"  in  small,  shallow  reservoirs  where  the  aquatic  vegetation  is 
thick  they  do  not  impart  any  characteristic  '  natural '  odor,  but 
they  may  produce  a  sort  of  vegetable  taste  and  a  disagreeable 
odor  due  to  decomposition,"  which  seldom  becomes  more  than 
"  decidedly  unpleasant,"  being  generally  a  moldy  or  musty 
odor  suggestive  of  a  damp  cellar.  "  The  floating  microscopic 
organisms,  or  the  plankton,  are  responsible  for  most  of  those 
peculiar  nauseating  odors  that  are  the  cause  of  complaint  in  so 
many  public-water  supplies.  In  most,  if  not  in  all,  cases  the 
odor  is  due  to  the  presence  of  an  oily  substance  elaborated  by 
the  organisms  during  their  growth."  Many  of  these  organisms 
are  very  delicate  and  are  disintegrated  by  passing  through 
water-pipes,  so  that  the  odor  is  greater  at  the  taps  than  at  the 
reservoir.  "  The  natural  odor  of  the  organisms  is  due  to  some 
oily  substance  analogous  to  those  substances  found  in  higher 
plants  and  animals,  and  that  give  the  odor  to  the  peppermint 
and  the  herring."  It  is  found  that  the  odor  of  a  given  oil  varies 
with  the  degree  of  dilution  in  character  as  v/ell  as  in  intensity. 
The  distinctive  odors  may  be  classified  as  aromatic,  grassy,  and 
fishy.  The  kind  given  by  each  of  the  more  common  offenders 
is  as  follows  : 


APPENDIX. 


559 


Organism. 


DiATOMACE^  {Plants). 
Asterionella 

Cyclotella 
Diatoma 
Meridion 
Tabellaria 

Protozoa  {Animals). 

Cryptomonas 
Mallomonas 


Cyanophyce.^  {Plants). 
Anabaena 

Rivularia 
Clathrocystis 
Coelosphserium 
Aphanizomenon 

Chlorophyce^  {Plants). 

Volvox 
Eudorina 
Pandorina 
Dictyosphaerium 

Protozoa  {Animals). 

Uroglena 
Synura 

Uinobryon 
Bursaria 
Peridinium 
Glenodinium 


Natural  Odor. 


Aromatic. 

Very    strong  ;     a    few     aromatic,    more    ge- 
ranium, most  fishy. 
Faintly  aromatic. 

Aromatic. 


Candied  violets. 

Aromatic;     violets;   but    the  most  abundant 
fishy. 

Grassy.     (Pig-pen  odor  when  decaying.) 

Most   important  of   the   class.     Grassy  and 
moldy;  green  corn;  nasturtiums,  etc. 
Grassy  and  moldy. 
Sweet,  grassy. 

Grassy. 


Fishy. 


Fishy. 
Faintly  fishy. 


Worst  of  the  class.     Fishy  and  oily. 
Very    bad.       Ripe     cucumbers;    bitter    and 
spicy  taste. 

Fishy,  like  rockweed. 

Irish  moss;  salt  marsh;  fishy. 

Fishy;  like  clam  shells. 

Fishy. 


It  cannot  be  stated  positively  whether  these  organisms  are 
injurious  to  health,  but  "  it  is  believed  that  such  organisms  are 
not  injurious, — certainly  not  to  persons  in  good  health  "  ;  but 
some  temporary  intestinal  disorder  may  be  caused,  especially 
to  young  children  and  invalids,  by  a  change  from  pure  water 
to  that  rich  in  organisms.  A  water  containing  less  than  lo 
millic^rams    of  solid    matter    from   Asterionella  to   a  glassful 


560  APPENDIX. 

would  be  unfit  to  drink  because  of  the  odor,  and  it  is  almost 
inconceivable  that  such  a  small  amount  of  organic  matter  could 
cause  trouble  unless  some  poisonous  principle  were  present, 
which  so  far  as  is  known  is  not  the  case. 

The  odors  caused  by  organic  matter  other  than  living 
organisms  are  generally  due  to  vegetable  matter  in  solution. 
Brown-colored  waters  have  a  sweetish-vegetable  odor  which 
varies  in  intensity  with  the  depth  of  color;  both  color  and 
odor  being  due  to  certain  glucosides,  of  which  tannin  is  an  ex- 
ample, extracted  from  leaves,  grasses,  mosses,  etc.,  and  being 
accompanied  by  a  slight  astringent  taste.  In  colorless  waters 
the  odors  of  this  class  are  usually  less  sweetish  and  more 
straw-like  or  peaty.  (For  a  full  treatment  of  this  subject  see 
Whipple's  excellent  "Microscopy  of  Drinking-water"  from 
which  the  above  was  largely  obtained.) 


INDEX. 


PACH 

Absorption,  Power  of,  various  soils gy 

Acre-foot,  Definition  of 29 

Air-escape  valves   , 424 

Air-lift,  Raising  water  by 360 

Air,  Removing,  from  suction-pipe 394,  494,  4^5 

Albuminoid  ammonia,  Definition  of 8 

Algse.  Effect  of,  in  water 16 

Alumina,  Use  of,  in  purification 302 

American  filters.  Cleaning 309 

"  "     ,  Coagulant  required  for 309 

"  "     ,  Cost  of 451 

"  "     ,  Definition  of 287,  304 

"  "     ,  Efficiency  of 306,308 

"  "     ,  Locating 3gg 

"  "     ,  Method  of  action 304 

"     .Operating 500 

"  "     ,  Regulating  chemicals  for 315 

Analysis,  Value  of 5,  501 

"        ,  chemical,  Units  used  in S 

Anchor-ice 202,  392,  493 

Anderson  process  of  purification ^n 

Angle  of  repose  of  soils 269 

Aqueduct,  Definition  of 1^3 

Artesian  well.  Definition  of 146 

Asphalt  for  lining  reservoirs 281 

Auxiliary  water-supplies 369 

Back-water,  Calculating  amount  of 215 

Bacteria,  Characteristics  of 10,  16 

"  in  ice 126 

"  "  mains 507 

"  "  rain-water gy 

"  "  streams 132,  134 

"       ,  Number  of,  in  water 17 

!        *'       ,  Removal  of,  by  filtration 292,  306,  308 

'        **  "         "     "    sedimentation iig 

"       ,  Size  of 10 

561 


562  INDEX. 

PACK 

Bacteriological  Analysis.     See  Analysis. 

Benches,  flume,  Cost  of 446,  461 

Bench-flume,  Definition  of I73 

Blow-offs 424 

Boiler  pressure  and  duty.  Relation  between 341 

room,  Arrangement  of 351 

Boilers,  Capacity  of 352 

"       ,  Description  of 352 

"       ,  Dimensions  of 353 

,  Efficiency  of 334 

"       ,  Foundations  for » 4^4 

Bridge-crossings,  Wrought-iron  pipe  for 420 

B.  T.  U.,  Definition  of 33i 

Bucket  pumps,  Description  of 322 

Canals,  Dimensions  of  several 182 

,  Head-works  for 170,  388 

"       ,  Location  of 171.  1S7 

"       ,  Percolation  from 172 

Cement-lined  pipe 420,  524 

Centrifugal  pumps,  Description  of 325 

Chemical  Analysis.     See  Analysis. 

Chemicals  for  purification,  Applying 315 

Chezy  formula 210 

Chimneys,  Constructing 4^4 

"  ,  Dimensions  of 354 

Chlorine,  Amount  of,  in  various  waters 13 

"        ,  normal,  Definition  of 14 

"        ,  Significance  of Q.  13 

"        ,  Sources  of 13 

Cholera,  Cause  of 16 

Cisterns,  Rain-water 58,  85 

Cistern- water,  Analyses  of 60 

Clark  process  for  softening  water 314 

Classification  of  matters  in  water 7 

Cleaning  reservoirs.  Method  of 4S7 

"  "  ,  Necessity  for 121 

Clearing  and  grubbing.  Cost  of 445.  457 

"  "  "         ,  Method  of 466 

Coagulants,  Use  of,  in  purification 302,  304,  309,  315 

Coefficients  for  pipes 219,  220 

"  "     rectangular  conduits 211 

"'  "     smooth  circular  conduits 210,  218 

"  "    wood-stave  pipe 220 

Collecting-pipe,  Definition  of 200 

"  '*    .Designing 200 

"  *'   .Locating » 395 


INDEX. 


563 


Collecting  rents 545 

Color  of  water.  Measurement  of I9)  55^ 

"         "     ,  Significance  of ig 

"     ,  Removing  from  water 307 

Compound  pumping-engine 330 

Concrete,  Cost  of 446 

"         ,  Mixing 456 

Condensing  engine 330 

Conduit,  Junction  of,  with  reservoir 165 

Conduits,  closed,  Construction  of 408 

"  '       ,  Dimensions  of  several 186 

"  "      ,  Location  of 168,  185,  197,  425 

"  "      ,  Strength  of 185 

"  "      ,  where  used  . 182 

"         ,  Cost  of . . . ., 447.  461 

"         ,  Curves  in 1S7,  427 

"         forcity  supplies 182 

"         ,  Grades  to  be  given 174 

"         ,  irrigation.  Maintaining 488,  508,  527,  530 

"         ,  Materials  used  for 171,  173 

"         ,  open,  Description  of 171 

"  "     ,  Construction  of 405 

"         ,  pressure,  Construction  of 409 

"         ,  Size  necessary  for 174,  i8r,  431 

"         ,  Velocity  of  flow  in ......    174 

"         ,  Waste-weirs   for iSi 

Consumption,  Amount  available  for,  from  watersheds 112 

of,  in  cities 34,  549,  550 

"  "         required  for 47 

"  ,  Maximum 37,  3^ 

"  of  water  by  crops 92 

"  per  capita  and  per  tap,  New  England 47 

"  "         "      ,  by  meter,  in  several  cities 46 

Contracted  vein.  Definition  of 222,  550 

Core-wall,  Purpose  of 270,  272 

Corporation  cocks 525 

Cost,  Estimating 445 

"     .     See  item  in  question. 

Covering  reservoirs 2S3 

Cranes,  water-.  Cost  of 449 

"      ,  for  street-sprinkling 431 

Cribs,  Filter 31  x 

"     ,  Intake 390 

"     ,  Underground 149,  311 

Crops,  Consumption  of  water  by 92 

Curb-cocks 52? 


564  INDEX. 

PAGE 

Current-meters,  Use  of 240 

Curves  in  pipe  lines 427 

"    pipes,  Friction-head  in 223,  551 

Cut-off  walls  in  embankments 272 

Dams,  brick.  Construction  of 246 

"     ,  Collecting  data  for  locating 377 

"     ,  concrete.  Construction  of 246 

"     ,  Constructing 456,  470 

"     ,  Curved 259 

"     ,  earth.  Data  of  several 276 

"  "     ,  Designing 268,  382 

"  "     ,  Where  applicable 243,  268 

"  "     .     See  also  embankments. 

"     ,  Estimating  volume  of 379 

"     ,  Height  of 259 

"     ,  Hydraulic  construction  of 277 

*•     ,  leaks  in,  Stopping 489 

"     ,  Locating 161,  377 

"     ,  masonry,  Conduits  through 245 

"  "         ,  Construction  of 245 

'•  "         ,  Data  of  several 260 

"  "  ,  Designing 247,  382 

"  "         ,  Foundations  for 243 

"  "  ,  Sections  of 255 

"  "         ,  where  applicable 242 

"  "         ,  Wing  walls  for 245 

"     ,  Materials  used  for 242,  379 

"     ,  Rock-fill 259,  264 

"     ,  timber.  Construction  of 263 

"  "      ,  Where  applicable 242,  243 

Dead-ends,  Disadvantages  of 195,  50S 

Designing  a  system,  Data  required  for 364 

Differential  plunger 322 

Direct-pumping  system 19S 

-indirect        "  198,375 

Distillation,  Purification  by 315 

Distribution  system.  Calculating  sizes  of 432 

"  "      ,  Definition  of 158 

"  "      for  city  supplies 189 

"  "       "    irrigation 187 

"  "      ,  Maintaining 11,5 

Drilling  wells 4P3 

Droughts,  Precipitation  during 7> 

Durability  of  a  water- works  system 544 

Duty  and  work  of  pumps.  Relation  between ....    342 

"     of  irrigating  water 30,  174 


INDEX. 


s6r 


Duty  of  pum ping-engines 331,  335,  341 

Dwelling,  Population  per,  sevcralcities 44 

Earth,  Angle  of  repose  of 269 

Economizer,  Use  of 334 

Electrical  purification 313 

Electricity,  Thawing  pipes  by 519 

Electric  motors  for  pumping 356 

Electrolysis  of  pipes.  Preventing 420,  529 

Embankments,  Constructing 273,  466 

"  "  conduits  through 275,  383 

"  ,  construction  of.  Superintending  the 454 

"  .  Cost  of 445,  457 

"  ,  Data  of  several 270 

"  .Designing 268 

"  ,  leaks  in,  Repairing 489 

"  ,  Materials  for 272 

Energy  of  moving  water 213 

Engines,  Compound  pumping- 330 

"       ,  Condensing 330 

"       ,  Duty  of 331 

"       ,  Horizontal  and  vertical 330 

"       ,  pumping,  Cost  of 450 

"       ,  Triple-expansion 330 

English  filters,  Action  of 292 

"     ,  Applicability  of 302 

"  "     .Cleaning 293.295,301,502 

"  "     .  Construction  of   291,  299,  301,  401 

"  "      ,  Covering  for 300 

"  "     ,  Definition  of 287,  290 

"  "     ,  Depth  of  water  on 293,294,299 

"  "     ,  Description  of 290 

"  "     .  Efficiency  of 301,552 

"  "     .Operating 502,552 

"  "  "  ,  cost  of 552 

"  "      ,  Precipitation  used  with 303 

"  "     ,  Rates  of  filtration  through 295,  296,  299 

"  "     .  Sand  for 296 

*'  "     ,  Size  of,  necessary 295 

"  "     .Under-draining 298 

"  "     ,  Washing  sand  of 300 

Evaporation,  Effect  of,  upon  run-off 93,  96 

"  from  reservoirs in,  117,  490 

"  "      snow 91 

"  "      soils 91,95 

**  "      water 89,117 

"  .  Latent  heat  of 332 

"  ,  Vermeule's  formula  for  determining 93 


566  INDEX. 

FAGS 

Excavating,  Cost  of 445.  457 

"  ,  Methods  of 466 

Excreta,  Composition  of  human 10 

Feed- water  heater.  Use  of 334 

Filter-plants,  Locating 376 

Filters,  American.     See  American  filters. 

,  Cost  of 451 

"      ,  English,     See  English  filters. 

,  Household 316 

"       ,  Worms 311 

Filtration,  Effect  of,  upon  health 20,  23 

"         ,  Intermittent.     See  Intermittent  filtration. 

in  the  United  States,  Data  of 318,552 

"         ,  Rates  of,  in  English  filters 295 

"         ,  Removing  iron  by 312 

Finances,  Water- works 539,  543 

Fire-hydrants.     See  Hydrants. 

Fire  service,   Maintaining 374 

Fire-streams,  Amount  of  water  required  for 40 

Fixtures,  Number  of  water,  per  capita ^ 37 

Flash-boards,  Use  of 259 

Floats,  Use  of 240 

Flow  of  water,  Effect  of  obstructions  upon 214 

"       "        "      in  very  smooth  pipes 218 

"       "       "     ,  Laws  of , 209,  216 

Flumes,  Construction  of 173,  406,  457 

,  Head-works  for 170 

Flushing-out  gates 185 

"    sluices 170 

Flywheel  pum ping-engine 328 

Forests,  Effect  of,  on  rainfall 60 

Freezing  of  mains 426 

"        ,  Purification  by 126 

Frozen  pipes.  Thawing 519 

Galvanized  iron  pipe 524 

Gas-eng.i;cs,  Cost  of  pumping  with 358 

,  Pumping  by 357.358 

Gasoline,  Cost  of  pumping  with 35S 

"        engines,  Pumping  by 357,  358 

Gate-house,  Reservoir 3S5 

Gates.     See  Valves. 

Goose-necks 525 

Gravity  system,  Definition  of 158 

Ground-storage,  Effect  of,  upon  run-off 94 

Ground-water,  Classification  of 140 

"  "     ,  Elevation  of gS,  97 


INDEX. 


567 


FACE 

Ground-water,  Flow  of gj^  136^  j^«  -- j 

"             "     ,  Health  fulness  of 23 

"             "     ,  Hydraulic  gradient  of i-y 

"             "     ,  Intercepting jcq 

"            "     ,  Natural  storage  of 153 

"             "     plants,  Designing -j- 

"             "     ,  Quality  of j^^ 

"     .  Quantity  of 136,140,152 

"             "     ,  Source  of t-. 

Grubbing  and  clearing,  Cost  of ..c 

Hardness,  Definition  of j2 

"         ,  Effects  of 12 

' '         ,  Test  for ccc 

Hard  water.  Softening -14 

Head-works,  Definition  of icg 


for  canals  and  flumes. 


170 


Heat,  Losses  of,  in  steam  pumping-plant 0-15 

Health,  Effect  of  water  upon 21,  23,  559 

High-duty  engine,  Definition  of too 

High-service,  Definition  of 105 

Hose,  fire.  Flow  through 231^  233 

Hydrants,  fire.  Cost  of ^^g^  ^5i 

"  "    ,  Description  of 420 

"  "    ,  Loss  of  head  in 232 

"  "    ,  Maintenance  of 431,  513    522 

"  "    ,  Rental  of 530 

"       Setting 429 

"      Testing    463 

Hydraulic  gradient,  Definition  of 225 

"  "         of  ground-water 137^  145 

"         power  for  pumping 354 

Ice,  Anchor  or  needle 202,  392 

"  ,  Impurities  in 126 

Impulse  of  moving  water 213 

Impurities  in  water,  Nature  of 2,  557 

Indirect- pumping  system ig3_  275 

Infiltration-galleries I4g^  3q8 

Inorganic  substances  found  in  water 8,  ir 

Intake-cribs 3go 

-pipes 201,  389,  392 

Intakes,  Designing 300 

"     ,   Location  of 200 

,   Maintaining 403 


Intermittent  filtration, 


21.4 


Iron,  Effect  of,  upon  water u 

"   ,  Removing,  from  water 3x2 

"  ,  Source  of,  in  water u 


568  INDEX. 

PACE 

Irrigation-conduits,  Maintaining 488,  508,  527,  530 

"        ,  Deep  wells  for 148 

"        ,  Water  required  for 29,  92,  488 

Isochlores 14 

Jet  ting-down  wells 482 

Jets,  Hydraulics  of 222,  550 

Joints,  Melting  lead 512 

"      ,  Pipe 311,  476 

Kutter's  formula 211 

Lakes,  Intakes  in 201 

Lake  water,  Characteristics  of 134 

"  "      ,  Healthfulness  of 23 

Lead  in  water,  Effect  of 14 

"     pipes 194,  524 

"   ,  Source  of,  in  water 14,  524 

Leaks  in  dams,  Repairing 489 

"        "    embankments,  Repairing 488,  489 

"       "    pipes.  Repairing 509 

"     ,  Waste  of  water  through 42,  43 

Life  of  a  water-works  system 544 

Lime,  Effect  of,  in  water 12 

Lining  for  reservoirs  and  embankments 270,  278,  382 

"  ,  Constructing 469 

"        "  "  "  "  ,  Cost  of 446 

Low  service,  Definition  of 195 

Magnesia,  Effect  of,  in  water 12,  13 

Mains,  city,  Calculating  size  of 433 

"  "    ,  Coating  for 194 

"  "    ,  Location  of 190,  193 

"  "    ,  Maintaining 195 

"       ,  Miles  of,  in  several  cities 45 

Maintenance  of  system,  Cost  of 544 

Maps  necessary  for  designing 364,  377 

Maps,  record.  Form  of 532 

Masonry,  Constructing 455,  470 

,  Cost  of 446,  457 

,  Maximum  height  for 252 

,  Strength  of 251 

,  Superintending  construction  of 455 

,  Weight  of 248 

Mass  diagram,  Calculating  storage  by 113 

Measuring  water.  Methods  of 235 

Mechanical  filters.     See  American  filters. 

Meteorological  districts  defined 63 

Meters,  Advantages  of  using 536 

"      ,  Data  concerning 537 

"      ,  Maintenance  of 523 

*'      ,  Number  of,  in  several  cities 45,  549 


INDEX. 


569 


Meters,  repairing,  Cost  of 523 


Records  of 


534 


"       ,  Venturi 239 

Microscope,  Use  of,  in  analysis 10 

Miner's  inch,  Definition  of igo 

Needle-ice.     Sec  Anchor-ice. 

Nitrates  in  water,  Formation  of 17 

"      ,  Meaning  of  term o 

Nitrites,  "  "      "     q 

Nitrogen,  Significance  of,  in  water 8 

Notes  of  pipe-lines .^51 

Nozzles,  Jets  from 231 

Odor  in  water.  Organisms  giving 557 

Oil-engines,  Cost  of  pumping  with 358 

for  pumping 357.353 

Organic  matter.  Composition  of g 

"  "       found  in  water 8,  14,  557 

"  "       in  water,  Effect  of 14,  557 

"       ,  Method  of  decomposition  of g 

Orifices,  Flow  through 236 

Oxygen,  Amount  of,  in  water g 

Percolation  in  various  soils 152,  2g7 

Piezometers 227 

Pipe  across  streams.  Laying 427,  47S 

Pipe,  cast-iron,  Laying 458,  463,  473 

.Cutting 475,512 

"     ,  Cost  of 447 

"     ,  city.  Calculating  size  of 433,  554 

"     ,  Depth  of  laying 426 

"     ,  laying,  Cost  of 447,  461 

"     lines.  Curves  in      427,  551 

"        "     ,  Records  of 461 

"     .Testing 461 

"     ,  riveted.  Constructing 453 

"     sections,  areas  of z,z.^ 

"    ,  Unloading,  from  cars 472 

"     ,  wood-stave,  Constructing 453 

,  Designing 421 

Pipes,  cast-iron,  Coating  for 413 

"  "       "     ,  Dimensions  of 412 

"     ,  Joints  of 411,476 

"  "       "     ,  Materials  for 413 

"  "       "    ,  Specials 414 

"     ,  Weight  of 412 

"     ,  Cement-lined 420 

"     ,  Cleaning 514 

"      ,  Electrolysis  of 528 

"     .  Flow  in 216,  554 

"     ,  frozen,  Thawing 510 


570  INDEX. 

PAGa 

Pipes,  leaks  in,  Repairing 509 

'     ,  Necessary  strengthof 410 

'     ,  Pressure  in 410 

'     ,  Quality  of  water  in 506 

,  service,  Materials  used  for 524 

'     ,  Temperature  in 506 

'     ,  Wooden 420 

'     ,  wrought-iron,  Applicability  of 419 

'  "  "     ,  Coating  for 418 

'  "  "     ,  Joints  for 416 

'  "  "     ,  Material  for 417 

'.  "  "    specials 417 

'  "  "    ,  Thickness  of 417 

*  "  "     ,  Weight  of 419 

Piston-pumps,  Description  of 321 

Pitometer,  Cole-Flad 511 

Plunger-pumps,  Description  of 321 

Polluted  waters,  Sanitary  qualities  of 20,  25 

Pollution  of  river- water 131 

Population,  Estimating  increase  of - 30 

"  per  dwelling,  several  cities 44 

"  per  mile  of  mains  and  per  tap 45 

Potsdam  sandstone,  Ground-water  from 137 

Power  Pumps,  Definition  of 327 

Precipitants,    Use    of,    in  purification 302 

Precipitation,  Annual,  by  districts  and  altitudes 62 

"  "in  meteorological  districts 61 

"  ,  Definition  of 303 

"  districts  defined 63,  71 

"  ,  Effect  of  altitude  upon 66 

"  ,  Estimating  future 68,  85 

"  ,  General  laws  of 66,  68 

"  in  dry  periods 78 

"  ,  Maximum  rates  of 80 

"  .Measuring Si 

"  ,  Monthly,  by  districts 70,  72 

"  "  ,  in  four  cities 71,  77 

"  "  ,  Laws  of 70,  74 

Pressure,  Hydraulic 206 

"         in  city  mains  in  United  States 45 

Pressure  in  pipes 410 

"         regulator.  Purpose  of 195 

"         required  in  city  mains 190 

Puddle-wall .- 270,  272 

Puddle,  Mixing  of 273,  46S 

Puddling,  Cost  of 446 

Pumping,  Air-lift  for 360 

"        ,  Cost  of 497 


INDEX.  57  J 

PAGB 

Pumping-engines,  Arrangement  of 342 

"  "        ,  Cost  of 450 

"  "        ,  high-duty,  Data  of 340 

"  "        ,     "        "     ,  Economy  of 339,342 

"  "        ,  Relation  of  boiler-pressure  to  duty 341 

*'        ,  Force  required  for 323,  320 

"        ,  Gas-,  gasoline-,  and  oil-engines  for 357 

"        plants,  Locating joo 

"  "      .Maintaining 496,534 

"  "      ,  steam.  Losses  of  heat  in 33c 

"  "       ,  Testing  efficiency  of ••335.337 

"      station,  Arrangement  of 351^  383 

"      system,  Definition  of 158 

"       ,  where  necessary 10^ 

"       ,  Windmills  for 360 

Pump-pits,  Constructing 482 

"        "   ,  where  necessary 347 

Pump-room,  Arrangement  of 350 

Pumps.  Action  of 323 

"     ,  deep  well.  Description  of 340 

"     ,  Deep  well,  where  necessary 200 

"     ,  Description  of 203,  321 

"     ,  Efficiency  of 327 

"     ,  Foundations  for 464 

"     ,  Location  of 204 

"     ,  Motive  power  for 202,  327,  354 

"     ,  Requirements  for 326 

"     ,  Single-acting 322 

Purification,  Anderson  process  of 313 

"  ,  Distillation 315 

"  ,  Electrical 313 

"  ,  Freezing  for 126 

"  ,  Methods  of 287,  316 

"  .     See  also  Filtration,  Sedimentation,  etc. 

Quality  of  river-water 13b 

"         "  surface-water 118 

"  water i 

"       "      in  mains 506 

"       "      "  reservoirs ng 

"     ,  Requisite 11,13,17,18,26 

Quantity  of  water  for  city  use 34 

"         "       "        "    suburban  use 33 

"         "        "       in  reservoir,  Maintaining 4go 

"         "       "      required  for  irrigation 29 

Railroads,  Pipes  under 428 

Rainfall.     See  Precipitation. 

Rain-gauges 81 


5/2 


INDEX. 


Rain-water,  Analyses  of 57 

"  "     ,  Definition  of 50 

"  "     .Impurities  found  in -6.  58 

"  "     ,  Storing 58,  83 

Rates,  Water 536,  541,  545,  54 > 

Reciprocating  pumps 321 

Records  at  reservoirs.  Keeping .    491,  534 

"        of  pipe-lines    461 

"         "   water-works  department 532 

Reservoirs,  Cleaning 121,  487 

Constructing 466 

Covered 283 

Depth  of 163 

distributing.  Capacity  of 169 

' '  ,  Location  of 169 

"  ,  Purpose  of 159 

Effect  of  ground-storage  upon 94,  98 

impounding.  Designing 379 

"  ,  Locating 371 

Lining  for 278 

Maintaining 485,  488,  490,  492 

Qualityof  water  in 119 

sites  of,  Cleaning 121,  164 

Spillways  for 166 

Staking  out  and  measuring 453 

storage,  Capacity  required  for 104,  106,  no,  113 

"        ,  Designing 162,  383,  491 

"        ,  Locating 160,  365 

"       ,  Purpose  of 159,  289 

Superintending  construction  of 454 

Temperature  of  water  in 121 

Turn-over  of  water  in 122 

water  in.  Preserving  purity  of 164,  165,  485 

Rivers,  Amount  of  flow  in 128 

"     ,  intakes  in,  Locating 201 

"      ,  Measuring  flow  of 366 

"     ,  Seepage  from 129 

"     ,  Underground  flow  of 129,  139 

River-water,  Definition  of 53 

"         "     ,  Effect  of,  upon  health 23 

"  "     ,  Pollution  of 131 

"  "      ,  Quality  of 130,  133 

Riveted  pipe.  Flow  in 221 

Rotary  pumps 325 

Run-off,  Amount  of 52,  98,  105 

"     "   .Definition  of 51.  98 

"     "   ,  Effect  of  bodies  of  water  upon. .. 103 


INDEX. 


Run-off,  Effect  of  evaporation  upon 93.  go 

"     "   ,       "       "    ground-storage  upon 94 

"      "    .Estimating 370 

"     "  from  storms 106 

"     "   ,  Methods  of  estimating 98,  108 

"      "   ,  Source  of 51 

"     "   ,  Storage  of 104 

St.  Peter  sandstone,  Ground-water  from 137 

Salt  water  for  street-sprinkling 369 

Sand  boxes ....  424 

"     filters.     See  English  filters. 

"     for  filters.  Size  of 291,  297 

"     ,  Rate  of  percolation  through . .    296 

Scale  in  boilers,  Cause  of 12 

Schmutzdecke,  Definition  of 292 

Scraping,  Cleaning  pipes  by 514 

Screens  for  intakes 384 

Sedimentation  basins,  Construction  of 401 

"                   "     ,  Location  of 400 

"                   "     ,  Size  of 289 

"             in  reservoirs 119,  505 

"  ,  Purification  by 288,  296,  302 

Seepage  from  canals 172 

"           "      reservoirs 112 

"           "      rivers 129 

"      ,  Remedies  for 173 

Service  connections,  Cost  of 545 

.  Making 524 

"     ,  Meaning  of 29,  188 

Sewage,  Pollution  caused  by 131 

"       pollution  of  water.  Effect  of 20 

Sheathing  wells 47g 

Silt,  Amount  of  transportable 216 

"  ,  Removing,  from  river-water 132 

Siphons 


187,  425 


Slip,  Definition  of 324 

Slopes  for  embankments 269 

Sluice-gates,  Illustration  of 386 

Sluices.  Flushing-out 170,  388 

Snow,  Analyses  of 58 

"      ,  Run-off  from 107 

Softening  hard  water 31^ 

Source  of  supply.  Selecting  the 365,  368 

Sources  of  supply  used  by  various  cities 55 

"  "   water I 

Specials,  Cast-iron ^i^ 

,  Locating 436 


574 


INDEX. 


Spillways,  Designing 167,  383 

"  ,  Location  of 166,  3S3 

"         ,  Maintaining 493, 

"         ,  Purpose  of 166 

Springs,  Developing  flow  of 152 

"       in  the  ocean 137 

"       ,  Sources  of 151 

Spring-water.  Character  of 151 

Sprinkling,  street,  Water-cranes  for • 431 

Standards  of  purity  of  water 11,  13,  17,  18,  26 

Standpipes,  Constructing 464 

"  ,  Cost  of 451 

,  Designing 436,  438 

"  .Dimensions  necessary  for 374,  437 

"  ,  Purpose  of igg 

"  .where  used 374,  437 

Statistics,  water-works,  Form  for 535 

Storage.  Natural 94,  153 

"       of  ground-water 153 

"       "   rain-water S3. 

"       "  surface-water 104,  109,  113 

"       Reservoirs.     See  Reservoirs. 

Storms,  Run-off  from io6- 

Streams,  Pipe-lines  across 427,  478- 

Suction-pipe  from  pump.  Location  of 389- 

Supply  obtainable  from  given  watershed 104 

Surface-water,  Definition  of 50 

"  "     ,  Effect  of,  upon  health 23 

'*  "     ,  Preserving  purity  of 119 

'•  "     ,  Quality  of 118 

"  "     .  Storage  of 104,  109 

Surveys  necessary  for  designing 162 

Systems,  Cost  of  maintaining 544 

"         .      "      "   ,  per  mile 45 

"         of  supply,  Outline  of 4 

"  "        "       used  in  the  United  States 204 

Tanks,  Water,  Designing 437 

"  "      ,  where  used 437 

Tapping  iron  pipes.  Methods  of 525 

Taps,  Number  of,  in  several  cities 45.  549 

Taste  in  water,  Organisms  giving 557 

Temperature  of  water  in  mains 506 

"  "        "       "  reservoirs 121,506 

Testing  pipe-lines 4<Ji 

Test  of  steam-pumping  engines 332,  335,  337 

Thawing  frozen  pipes 519 

Timber  in  place.  Cost  of 446 

Tin-lined  pipe 524- 


INDEX. 


575 


PAG  a 

Trenches,  Cost  of 447 

"         ,  Excavating 459,  472 

"         ,  Laying  out 459 

Triple-expansion  engine 330 

Tubercles,  Removing,  from  pipes 514 

Tuberculation,  Effect  of.onflowin  pipes 216,  519 

Turbidity  in  irrigating  water 27 

,  Measurement  of 19.556 

"        ,  Removing 307,  375 

Turn-over  in  reservoirs  and  lakes 122,  166 

Typhoid  fever.  Cause  of e.  . .   16,  20,  119 

"  "    ,  Death-rates  from 24,  5'  7 

"  "    from  ground-water 155 

"  "    ,  Loss  to  community  due  to 25 

"    ,  Nature  of 17 

Underground  flow  of  rivers 129,  139 

Units  used  in  chemical  analyses 8 

Valve-boxes,  Setting 478 

Valves,  Cost  of 447,  461 

"     ,  Effect  of  partially  closing 224,  551 

"      .Kinds  used  on  pipe-lines 42S 

"     ,  Maintenance  of 522 

"     on  city  mains.  Location  of igi,  193 

"     ,  Pump 324 

Velocity- head.  Definition  of 222 

Velocity  of  flow  of  ground-water 143 

Waste  of  water,  Extent  of 41 

,  Preventing 49°.  523.  535.  545 

Waste -weirs.  Designing 167 

"  "    ,  Location  of 166 

"     ,  Purpose  of 166,  181 

Water-hammer 229 

Watershed,  Care  of  a 485,  490 

"        "    ,  Selecting,  fora  system 370 

Watersheds,  Preserving  cleanness  of 119 

Water- tank,  Purpose  of 199 

Waves,  Height  of 168 

Weight  of  water 235 

Weirs,  Flow  over 237 

Well-casing,  Pipe  for 484 

Wells,  Cost  of 449 

deep,  Characteristics  of 148 

"     ,  Construction  of 396,  482 

"     ,  Cities  using 147 

"     ,  Location  of 141,  146,  395 

Depth  of 146 

dug,  Constructing 398,  464,  479 

driven,  Constructing 4S2 


57^  INDEX. 


PAGE 


Wells,  Effect  of  pumping  upon 145,  149, 

"  "       '     tides  upon 13^ 

"     for  irrigation 14S 

"     ,  Freezing  of 494 

"     ,  Locating 366,  395 

"     ,  Maintaining 4g4_ 

"     ,  Measuring  flow  of 367 

"     ,  Permanency  of  flow 149 

"     ,  Repairing  leaks  in 494 

"     ,  Shallow 139,  141 

"     ,  Yield  of 148,  149 

Well-waters,  Analyses  of 156 

"  "      ,  Sources  of  various 147 

Wind-mills  for  pumping 360- 

Wood-stave  pipe,  Designing 421 

"  "  "    ,  Flow  in 22CV 

Worms  filters 311 

Yield,    Definition  of 51 

"     .     See  Run-off. 

Zinc  pipes 194 


CHAS.  MILLAR  ^  SON,  Selling  Agents,  Utica,  N.  Y. 


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tings, 

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Lead,  Jute,  etc. 


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AND 

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Duhem's  Thermodynamics  and  Chemistry.     (Burgess.) 8vo,  4  00 

Flather's  Dynamometers,  and  the  Measurement  of  Power izmo,  3  00 

Gilbert's  De  Magnete.     (Mottelay.) 8vo,  2  50 

Hanchett's  Alternating  Currents  Explained i2mo,  i  00 

Hering's  Ready  Reference  Tables  (Conversion  Factors) i6mo,  morocco,  2  so 

Hohnan's  Precision  of  Measurements 8vo,  2  00 

Telescopic  Mirror-scale  Method,  Adjustments,  and  Tests Large  8vo,  75 

9 


Landauer's  Spectrum  AnalysiB.    (Tingle.) 8vo,  3  o« 

L«  Chatelier's  High-temperature  Measurements.  (Boudouard — Bxirgess.)i2mo,  3  00 

Lob's  Electrolysis  and  Electrosynthesis  of  Organic  Compounds.  (Lorenz.)  i2mo,  i  00 

•  Lyons's Treatise  on  Electromagnetic  Phenomena.     Vols.  I.  and  II.  livo,  each,  600 

•  Michie.     Elements  of  Wave  Motion  Relating  to  Sound  and  Light 8vo,  4  00 

Niaudet's  Elementary  Treatise  on  Electric  Batteries.     (Fishoack. ) i2mo,  350 

•  Rosenberg's  Electrical  Engineering.   (Haldane  Gee— Kinzbrunner.) 8vo,  i  50 

Ryan,  Norris,  and  Hoxie's  Electrical  Machinery.     VoL  L 8vo,  2  9* 

Thurston's  Stationary  Steam-engines 8vo,  a  50 

•  Tillman's  Elementary  Lessons  in  Heat 8vo,  i  90 

Tory  and  Pitcher's  Manual  of  Laboratory  Physics Small  8vo,  a  00 

Hike's  Modern  Electrolytic  Copper  Refining 8vo,  3  o« 

LAW. 

•  Davis's  Elements  of  Law 8to,  a  50 

•  Treatise  on  the  Military  Law  of  United  States 8vo,  7  ©• 

•  Sheep,  7  50 

Manual  for  Courts-martial i6mo,  morocco,  1  50 

Wait's  Engineering  and  Architecttiral  Jurisi>rudence 8vo,  6  00 

Sheep,  6  50 
Law  of  Operations  Preliminary  to  Construction  in  Engineering  and  Archi- 
tecture      8vo,  5  o« 

Sheep,  5  50 

Law  of  Contracts 8vo,  3  o« 

Winthrop's  Abridgment  of  Military  Law lamo,  a  5« 

MANUFACTURES. 

Bamadou's  Smokeless  Powder — Ifitro-cellulose  and  Theory  of  the  Cellulose 

Molecule lamo,  a  s* 

BoUand's  Iron  Founder i2mo,  a  54 

"  The  Iron  Founder,"  Supplement lamo,  a  S* 

Encyclopedia  of  Founding  and  Dictionary  of  Foundry  Terms  Used  in  the 

Practice  of  Moulding lamo,  3  00 

Sissler's  Modem  High  Explosives 8vo,  4  00 

SSront's  Enzymes  and  their  Applications.     (Prescott.) 8vo,  3  00 

Fitzgerald's  Boston  Machinist i8mo,  i  00 

Ford's  Boiler  Making  for  Boiler  Makers i8mo,  i  o« 

Hopkins's  OU-chemists'  Handbook 8vo,  3  00 

Keep's  Cast  Iron 8vo,  a  $m 

Leach's  The  Inspection  and  Analysis  of  Food  with  Special  Reference  to  State 

ControL     (In  preparatum.) 
Matthews's  The  Textile  Fibres.    (In  preta.) 

Metcalf's  SteeL     A  Manual  for  Steel-users   lamo,  a  o* 

Metcalfe's  Cost  of  Manufactures — And  the  Administration    of  Workshops, 

Public  and  Private 8vo,  5  o« 

Meyer's  Modern  Locomotive  Construction 4to,  xo  o* 

Morse's  Calculations  used  in  Cane-sugar  Factories i6mo,  morocco,  i  50 

•  Reisig's  Guide  to  Piece-dyeing 8vo,   as  oc 

Sabin's  Industrial  and  Artistic  Technology  of  Paints  and  Varnish 8vo,  3  00 

Smith's  Press-working  of  Metals 8vo,  3  00 

Spalding's  Hydraulic  Cement i2mo,  a  o« 

Spencer's  Handbook  for  Chemists  of  Beet-sugar  Houses i6mo,  morocco,  3  00 

HandbooK  tor  sugar  Manufacturers  and  their  Chemists.. .  i6mo.  morocco,  a  o* 
Taylor  and  Thompson's  Treatise  on  Concrete,  Plain  and  Reinforced.     (In 

presi.) 

Thonton's  Manual  of  Steam-boilers,  their  Designs,  Construction  and  Opera- 
tion  8vo,    5  o« 

10 


•  Walke'«  Lectures  on  Explosives 8vo,  4  o* 

West's  American  Foundry  Practice i2mo,  a  50 

Moulder's  Text-book i2ino.  a  50 

Wiechmaan's  Sugar  Analysis Small  8vo,  a  50 

Wolff's  Windmill  as  a  Prime  Mover 8vo,  3  o* 

Woodbury's  Fire  Protection  of  Mills 8vo,  a  5* 

Wood's  Rustless  Coatings:  Corrosion  and  Electrolysis  of  Iron  and  Steel.  .  .8vo,  4  00 

MATHEMATICS. 

Baker's  Elliptic  Functions 8vo,  i  50 

•  Bass's  Elements  of  Differential  Calculus lamo,  4  o* 

Brifgs's  Elements  of  Plane  Analytic  Geometry lamo,  i  00 

Compton's  Manual  of  Logarithmic  Commutations lamo,  i  50 

Davis's  Introduction  to  the  Logic  of  Algebra 8vo,  i  50 

•  Dickson's  College  Algebra Large  lamo,  I   S« 

•  Answers  to  Dickson's  College  Algebra 8vo,  paper,  25 

•  Introduction  to  the  Theory  of  Algebraic  Equations    Large   lamo,  I   3$ 

Halsted's  Elements  of  Geometry 8vo,  I   75 

Elementary  Synthetic  Geometry 8vo,  I   50 

Rational  Geometry lamo, 

•  Johnson's  Three-place  Logarithmic  Tables:    Vest-pocket  size paper,  15 

100  copies  for  5  00 

•  Mounted  on  heavy  cardboard,  8X10  inches,  as 

10  copies  for  a  00 

Elementary  Treatise  on  the  Integral  Calculus Small  8vo,  i  so 

Curve  Tracing  in  Cartesian  Co-ordinates lamo,  i  00 

Treatise  on  Ordinary  and  Partial  Differential  Equations Small  8vo,  3  5* 

Theory  of  Errors  and  the  Method  of  Least  Squares lamo,  i  50 

•  Theoretical  Mechanics lamo,  3  00 

Laplace's  Philosophical  Essay  on  Probabilities.     (Truscott  and  Emory.)  lamo,  2  00 

•  Ludlow  and  Bass.     Elements  of  Trigonometry  and  Logarithmic  and  Other 

Tables 8vo,  3  00 

Trigonometry  and  Tables  published  separately Each,  a  00 

•  Ludlow's  Logarithmic  and  Trigonometric  Tables 8vo,  i  00 

Maurer's  Technical  Mechanics 8vo,  4  00 

Merriman  and  Woodward's  Higher  Mathematics 8vo,  5  00 

Merriman's  Method  of  Least  Squares 8vo,  a  00 

Rice  and  Johnson's  Elementary  Treatise  on  the  Differential  Calculus. Sm.,  Svo,  3  00 

Differential  and  Integral  Calculus,     a  vols,  in  one Small  8vo,  2  50 

Sabin's  Industrial  and  Artistic  Technology  of  Paints  and  Varnish 8vo,  3  00 

Wood's  Elements  of  Co-ordinate  Geometry 8vo,  a  00 

Trigonometry:  Analytical,  Plane,  and  Spherical lamo,  1  oe 

MECHANICAL   EKGnTEERING. 
MATERIALS  OF  EKGIWEERIHG,  STEAM-ENGINES  AND  BOILERS. 

Bacon's  Forge  Practice lamo,  i  50 

Baldwin's  Steam  Heating  for  Buildings lamo,  a  so 

Barr's  Kinematics  of  Machinery Svo,  a  50 

•  Bartlett's  Mechanical  Drawing 8vo,  3  00 

•  "                 "                "         Abridged  Ed Svo,  i  s« 

Benjamin's  Wrinkles  and  Recipes lamo,  2  00 

Carpenter's  Experimental  Engineering Svo,  6  00 

Heating  and  Ventilating  Buildings Svo,  4  o« 

Gary's  Smoke  Suppression  in  Plants  tising  Bituminous  CoaL      (/n  prep- 
aration.) 

Clerk's  Gas  and  Oil  Engine Small  Svo,  4  00 

Coolidge's  Manual  of  Drawing Svo,    paper,  i  oe 

11 


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00 

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2 

00 

5 

00 

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50 

3 

00 

2 

00 

3 

00 

I 

50 

Coolidge  and  Freeman's  Elements  of  General  Drafting  for  Mechanical  En- 
gineers.    (In  press.) 

Cromwell's  Treatise  on  Toothed  Gearing i2mo,    1  50 

Treatise  on  Belts  and  Pulleys i2mo,    I  50 

Durley's  Kinematics  of  Machines 8vo,    4  CO 

Flather's  Dynamometers  and  the  Measurement  of  Power i2mo,    3  00 

Rope  Driving i2mo,    2  00 

Gill's  Gas  and  Fuel  Analysis  for  Engineers i2mo,    x  25 

Hall's  Car  Lubrication i2mo,    i  00 

Bering's  Ready  Reference  Tables  (Conversion  Factors) i6mo,  morocco,    2  50 

Button's  The  Gas  Engine 8vo,    5  00 

Jones's  Machine  Design: 

Part    I. — Kinematics  of  Machinery 8vo, 

Part  II. — Form,  Strength,  and  Proportions  of  Parts 8vo, 

Kent's  Mechanical  Engineer's  Pocket-book i6mo,    morocco, 

Kerr's  Power  and  Power  Transmission 8vo, 

Leonard's  Machine  Shops,  Tools,  and  Methods.     (In  prens.) 

MacCord's  Kinematics;  or.  Practical  Mechanism Svo, 

Mechanical  Drawing 4to, 

Velocity  Diagrams Svo, 

Mahan's  Industrial  Drawing.    (Thompson.) 8vo, 

Poole's  Calorific  Power  of  Fuels Svo, 

Reid's  Course  in  Mechanical  Drawing Svo. 

Text-book  o(  Mechanical  Drawing  and  Elementary  Machine  Design.  .Svo, 

Richards's  Compressed  Air i2mo, 

Robinson's  Principles  of  Mechanism Svo,    3  00 

Schwamb  and  Merrill's  Elements  of  Mechanism.     (In  press.) 

Smith's  Press-working  of  Metals   Svo,    3  00 

Thurston's  Treatise  on    Friction   and    Lost  Work   in    Machinery   and    Mill 

Work Svo, 

Animal  as  a  Machine  and  Prime  Motor,  and  the  Laws  of  Energetics.  i2mo, 

Warren's  Elements  o?  Machine  Construction  and  Drawing 870, 

Weisbach's  Kinematics  and  the  Power  of  Trarsmission.      Berrmann — 

Klein.) Svo, 

Machinery  of  Transmission  and  Governors.     (Berrmann — Klein.).  .8vo, 

BydrauUcs  and  Bydraulic  Motors.     (Du  Bois.) Svo, 

Wolfi's  Windmill  as  a  Prime  Mover Svo, 

Wood's  Turbines   Svo, 

MATERIALS  OF  ENGINEERING. 

Bovey's  Strength  of  Materials  and  Theory  of  Structures Svo,    7  50 

Burr's  Elasticity  and  Resistance  of  the  Materials  of  Engineering.     6th  Edition, 

Reset Svo , 

Church's  Mechanics  of  Engineering Svo, 

Johnson's  Materials  of  Construction Large  Svo, 

Keep's  Cast  Iron Svo, 

Lanza's  Applied  Mechanics Svo, 

Martens's  Bandbook  on  Testing  Materials.     (Benning.) Svo, 

Merriman's  Text-book  on  the  Mechanics  of  Materials Svo, 

Strength  of  Mater'als i2mo, 

Metcalf's  Steel.     A  Manual  for  Steel-users i2mo. 

Sabin's  Industrial  and  Artistic  Technology  of  Paints  and  Varnish Svo, 

Smith's  Materials  of  Machines i2mo, 

Thurston's  Materials  of  Engineering 3  vols  ,  Svo, 

Part   II.—  Iron  and  Steel Svo, 

Part  in. — A  Treatise  on  Brasses,  Bronzes,  and  Other  AUoys  and  their 
Constituents Svo 

Text-book  of  the  Materials  of  Construction Svo, 

13 


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00 

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00 

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5 

00 

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00 

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50 

7 

SO 

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00 

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00 

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00 

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00 

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Wood's  Treatise  on  the  Resistance  of  Materials  and  an  Appendix  on  the 

Preservation  of  Timber gvo,  2  00 

Elements  of  Analytical  Mechanics 8vo,  3  00 

Wood's  Rustless  Coatings:  Corrosion  and  Electrolysis  of  Iron  and  Steel. .  .8vo,  4  00 


STEAM-ENGINES  AND   BOILERS. 

Carnot's  Reflections  on  the  Motive  Power  of  Heat.     (Thurston.) izmo,    1   50 

Dawson's  "Engineering"   and  Electric  Traction  Pocket-book.  .  t6mo,  mor.,    5  00 

Ford's  Boiler  Making  for  Boiler  Makers i8mo,    i  00 

GoBs's  Locomotive  Sparks    8 vo ,    2  00 

Bemenway's  Indicator  Practice  and  Steam-eng'ne  Economy i2mo,    2  00 

Hntton'n  Mechanical  EngLneerlng  of  Power  Plants 8vo,    5  oo 

Heat  and  Heat-engines 8vo.    5  00 

Kent's  Steam-bo'ler  Economy 8vo,    4  00 

Kneass's  Practice  and  Theory  of  the  Injector 8vo     i  50 

UacCord's  Slide-valves 8vo,    2  00 

Meyer's  Modern  Locomotive  Construction 4to,    10  00 

Peabody's  Manual  of  the  Steam-engine  Indicator i2mo,    i   50 

Tables  of  the  Properties  of  Saturated  Steam  and  Other  Vapors 8vo,    i  00 

Thermodynamics  of  the  Steam-engine  and  Other  Heat-engines 8vo,    5  00 

Valve-gears  for  Steam-engines 8vo,    2  50 

Peabody  and  Miller's  Steam-boilers 8vo,    4  00 

Pray'i  Twenty  Years  with  the  Indicator Large  8vo,    2  50 

Pupln's  Thermodynamics  of  Reversible  Cycles  in- Gases  and  Saturated  Vapors. 

(Osterberg.) i2mo,   i   25 

Reagan's  Locomotives  :  Simple,  Compound,  and  Electric izmo,  2  50 

Rontgen's  Principles  of  Thermodynamics.     (Du  Bois.) 8vo,    5  00 

Sinclair's  Locomotive  Engine  Running  and  Management i2mo,    2  00 

Smart's  Handbook  of  Engineering  Laboratory  Practice i2mo,    2  50 

Snow's  Steam-boiler  Practice 8vo,    3  00 

Spangler's  Valve-gears 8vo,    2  50 

Notes  on  Thermodynamics i2mo,    i  00 

Spangler,  Greene,  and  Marshall's  Elements  of  Steam-engineering 8vo,    3  00 

Thurston's  Handy  Tables 8vo.    i    50 

Manual  of  the  Steam-engine 2  vols.   8vo,  10  00 

Part  I. — History,  Structuce,  and  Theory . .  .8vo,    6  00 

Part  n. — Design,  Construction,  and  Operation 8vo,    6  00 

Handbook  of  Engine  and  Boiler  Trials,  and  the  Use  of  the  Indicator  and 

the  Prony  Brake 8vo      5  00 

Stationary  Steam-engines 8vo,    2  50 

Steam-boiler  Explosions  in  Theory  and  in  Practice. . . .' i2mo     1  50 

Manual  of  Steam-boilers ,  Their  Designs,  Construction,  and  Operation .  8vo,    5  00 

Weisbach's  Heat,  Steam,  and  Steam-engines.     (Du  Bois.) 8vo,    5  00 

Whitham's  Steam-engine  Disign 8vo,    s  00 

Wilson's  Treatise  on  Steam-boilers.     (Flather.) i6mo,    2  50 

Wood's  Thermodynamics    Heat  Motors,  and  Refrigerating  Machines. . .  .8vo,    4  00 


MECHANICS    AND  MACfflNERY. 

Barr's  Kinematics  of  Machinery 8vo,  2  50 

Bovey's  Strength  of  Materials  and  Theory  of  Structures 8vo,  7  50 

Chase's  The  Art  of  Pattern-making i2mo,  2  50 

ChordaL — Extracts  from  Letters i2mo,  2  00 

Church's  Mechanics  of  Engineering 8vo,  6  00 

Notes  and  Examples  in  Mechanics 8vo,  2  00 

13 


Compton's  First  LeBsont  in  MeUl-working lamo,  i  50 

Compton  and  De  Groodt't  The  Speed  Lathe lamo,  i  50 

Cromwell's  Treatise  on  Toothed  G«aring i2mo,  i  50 

Treatise  on  Belts  and  PuUeyi lamo,  i  50 

Dana's  Text-book  of  Elementary  Mechanics  for  the  Use  of  Colleges  and 

Schools lamo,  i  50 

Dingey's  Machinery  Pattern  Making lamo,  a  00 

Dredge's   Record  of  the  Transportation  Exhibits    Building  of   the   World's 

Coliunbian  Exposition  of  1893 4to,  half  morocco,  5  00 

Du  Boit's  Elementary  Principles  of  Mechanics: 

VoL     I. — Kinematics 8vo,  3  50 

Vol.    n. — Statics 8vo,  4  00 

Vol.  III.— Kinetics 8vo,  3  50 

Mechanics  of  Engineerinc.     VoL   I Small  4to,  7  50 

VoL  n. Small  4to,  10  00 

Durley'a  Kinematics  of  Machines   8vo,  4  00 

Fitzgerald's  Boston  Machinist i6mo,  i  00 

Flather's  Dynamometers,  and  the  Measurement  of  Power lamo,  3  00 

Rope  Driving lamo,  a  00 

Con's  Locomotive  Sparks 8vo  a  00 

Hall's  Car  Lubrication lamo,  x  00 

Holly's  Art  of  Saw  Filing i8mo.  75 

*  Johnson's  Theoretical  Mechanics lamo,  3  00 

Statics  by  Graphic  and  Algebraic  Methods.  .*. 8vo,  a  00 

Jones's  Machine  Design: 

Part   I. — Kinematics  of  Machinery 8vo,  i  50 

Part  n. — Form,  Strength,  and  Proportions  of  Parts 8vo,  3  00 

Kerr's  Power  and  Power  Transmission 8vo, 

Lanza's  Applied  Mechanics 8to, 

Leonard  s  Machine  Shops,  Tools,  and  Methods,     (/n  prett.) 

MacCord's  Kinematics:  or,  Practical  Mechanism 8vo, 

Velocity  Diagrams 8vo, 

Maurer's  Technical  Mechanics 8vo, 

Merriman's  Text-book  on  the  Mechanics  of  Materials 8to, 

•  Michie's  Elements  of  Analytical  Mechanics 8to, 

Reagan's  Locomotives:  Simple,  Compound,  and  Electric lamo, 

Reid's  Course  in  Mechanical  Drawing 8vo,  a  00 

Text-book  of  Mechanical  Drawing  and  Elementary  Machine  Design.  .8vo,  3  00 

Richards's  Compressed  Air lamo,  i  50 

Robinson's  Principles  of  Mechanism 8to,  3  00 

Ryan,  Norris,  and  Hoxie's  Electrical  Machinery.     Vol.  1 8vo,  a  5* 

Schwamb  and  Merrill's  Elements  of  Mechanism,     (/n  prttt.) 

Sinclair's  Locomotive-engine  Running  and  Management lamo,  a  00 

Smith's  Press-working  of  Metals 8vo,  3  00 

Materials  of  Machines lamo,  i  00 

Spangler,  Greene,  and  Marshall's  Elements  of  Steam-engineering 8vo,  3  00 

Thurston's  Treatise  on  Friction  and  Lost  Work  in  Machinery  and  Mill 

Work 8vo,  3  00 

Animal  as  a  Machine  and  Prime  Motor,  and  the  Laws  of  Energetics.  I  a  mo,  i  00 

Warren's  Elements  of  Machine  Construction  and  Drawing 8vo,  7  50 

Weisbach's    Kinematics    and    the  Power  of    Transmission.     (Herrmann — 

Klein.) 8vo,  500 

Machinery  of  Transmission  and  Governors.     (Herrmann — Klein.). 8vo,  5  00 

Wood's  Elements  of  Analytical  Mechanics 8vo,  3  00 

Principles  of  Elementary  Mechanics lamo,  i  as 

Turbines 8vo,  a  50 

The  World's  Columbian  Exposition  of  1893 4to,  i  00 

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METALLURGY. 

Eglefton's  Metallurgy  of  SilTer,  Gold,  and  Mercury: 

VoL   I.— SUver 8to 

VoL    II. — Gold  and  Mercury 8vo 

•*  Iles's  Lead-smelting.     (Postage  0  cents  additionaL) lamo 

Keep's  Cast  Iron 8vo 

Kunhardt's  Practice  of  Ore  Dressing  in  Europe 8vo 

Le  Chatelier's  High-temperature  Measurements.  (Boudouard — Burgess.) .  lamo,  3  00 

Metcalf' s  SteeL     A  Manual  for  Steel-users lamo 

Smith's  Materials  of  Machines i2mo 

Thurston's  Materials  of  Engineering.     In  Three  Parts 8to 

Part   II. — Iron  and  Steel Sto 

Part  ni. — A  Treatise  on  Brasses,  Bronzes,  and  Other  Alloys  and   their 

Constituents 8to 

Hike's  Modem  Electrolytic  Copper  Refining 8vo 

MINERALOOY. 
Barringer's  Description  of  Minerals  of  Commercial  Valus.     Oblong,  morocco 

Boyd's  Resources  of  Southwest  Virginia 8to 

Map  of  Southwest  Virginia Pocket-book  form 

Brush's  Manual  of  Determinative  Mineralogy.     (Penfield.) 8to 

CtMSter's  Catalogue  of  Minerals Sto,  paper 

Ck)th 

Dictionary  of  the  Names  of  Minerals 8to 

Dana's  System  of  Mineralogy Large  8to,  half  leather. 

First  Appendix  to  Dana's  New  "System  of  Mineralogy." ....  Large  8to 

Text-book  of  Mineralogy 8vo 

Minerals  and  How  to  Study  Them . . . : lamo 

Catalogue  of  American  Localities  of  Minerals Large  8to 

Manual  of  Mineralogy  and  Petrography lamo 

Bakle's  Mineral  Tablet. 8vo 

Bgleston's  Cataktgue  of  Minerals  and  Synonyms 870 

Bussak's  The  Determination  of  Rock-forming  Minerals.     (Smith.)  Small  8to 
Merrill's  Non-metallic  Minerals:  Their  Occurrence  and  Ui«t. 8to 

*  Penfield's  Notes  on  Determinatire  Mineralogy  and  Record  of  Mineral  Tests. 

8to,  paper, 

Rotenbusch's   Microscopical   Physiography   of   the   Rock-making   Minerals 

(Iddings.) 8to 

*  Tillman's  Text-book  of  Important  Minerals  and  Docks 8to 

Williams's  Manual  of  Lithology 8vo 

MiiraiG. 

Beard's  Ventilation  of  Mines lamo 

Boyd's  Resources  of  Southwest  Virginia 8vo 

Map  of  Southwest  Virginia Pocket-book  form 

*  Drinker's  Tunneling,  Explosive  Compounds,  and  Rock  Drills. 

4to,  half  morocco, 

Biasler's  Modem  High  Explosires ^ 8vo 

Fowler's  Sewage  Works  Analyses lamo 

Goodyear's  Coal-mines  of  the  Western  Coast  of  the  United  States lamo 

Ihlseng's  Manual  of  Mining .    8to 

**  Ues's  Lead-smelting.     (Postage  gc.  additionaL) lamo 

Kunhardt's  Practice  of  Ore  Dressing  in  Europe 8to 

O'DriscoU's  Notes  on  the  Treatment  of  Gold  Ores 8to 

*  Walke's  Lectures  on  Explosives 8to 

Wilson's  Cyanide  Processes lamo 

Chlorination  Process lamo 

Hydraulic  and  Placer  Mining lamo 

Treatise  on  Practical  and  Theoretical  Mine  Ventilation lamo 

15 


00 

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50 

00 

00 

90 

00 

00 

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50 

4  00 


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50 


as 

00 

00 

00 

50 

00 

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50 

00 

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50 

SO 

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SANITARY  SCIENCE. 

Copeland's  Manual  of  Bacteriology.     (In  ■prtparation.) 

Folwell's  Sewerage.     (Designing,  Construction  and  Maintenance.; 8vo,  3  00 

Water-supply  Engineering 8vo,  4  00 

Fuertes's  Water  and  Public  Health lamo,  i  50 

Water-filtration    Works i3mo,  2   50 

Gerhard's  Guide  to  Sanitary  House-inspection i6ino,  i  00 

Goodrich's  Economical  Disposal  of  Town's  Refuse Demy  Sto.  3  59 

Hazen's  Filtration  of  Public  Water-supplies 8vo,  3  00 

Kiersted's  Sewage  Disposal i2mo,  i  25 

Leach's  The  Inspection  and  Analysis  of  Food  with  Special  Reference  to  State 

ControL     {In  preparation.) 
Mason's    Water-supply.     (Considered    Principally    from    a    Sanitary    Stand- 
point.)    3d  Edition,  Rewritten Svo,  4  o« 

Examination  of  Water.     (Chemical  and  BacteriologicaL ) i2mo,  i  25 

Merriman's  Elements  of  Sanitary  Engineering     Svo,  a  00 

Nichols's  Water-supply.     (Considered  Mainly  from  a  Chemical  and  Sanitary 

Standpoint.)     (1883.) Svo,  2  50 

Ogden's  Sewer  Design i2mo,  2  00 

Prescott  and  Winslow's  Elements  of  Water  Bacteriology,  with  Special  Reference 

to  Sanitary  Water  Analysis I2m0;  i   25 

•  Price's  Handbook  on  Sanitation i2mo,  i  50 

Richards's  Cost  of  Food.     A  Study  in  Dietaries i2mo,  i  00 

Cost  of  Living  as  Modified  by  Sanitary  Science i2mo,  1  00 

Richards  and  Woodman's  Air,  Water,  and  Food  from  a  Sanitary  Stand- 
point   Svo,  a  00 

•  Richards  and  Williams's  The  Dietary  Computer Sto,  i  50 

Rideal's  Sewage  and  Bacterial  Purification  of  Sewage Svo,  3  50 

Tumeaure  and  Russell's  Public  Water-supplies 8vo,  5  00 

Whipple's  Microscopy  of  Drinking-water Svo,  3  50 

Woodhull's  Notes  and  Military  Hygiene i6mo,  i  50 

MISCELLANEOUS. 

Barker's  Deep-sea  Soundings Svo,  2  00 

Emmons's  Geological  Guide-book  of  the  Rocky  Mountain  Excursion  of  the 

International  Congress  of  Geologists Large  Svo  i  50 

Ferrel's  Popular  Treatise  on  the  Winds Svo  4  00 

Haines's  American  Railway  Management i2mo,  3  50 

Mott's  Composition,  Digestibility,  and  Nutritive  Value  of  Food.   Mounted  chart,  i  as 

Fallacy  of  the  Present  Theory  of  Sound i6mo  i  00 

Ricketts's  History  of  Rensselaer  Polytechnic  Institute,  1834-1S94.  Small  Svo,  3  00 

Rotherham's  Emphasized  New  Testament Large  Svo,  2  00 

Steel's  Treatise  on  the  Diseases  of  the  Dog Svo,  3  50 

Totten's  Important  Question  in  Metrology Svo  3  59 

The  World's  Columbian  Exposition  ot  1893 4to,  i  00 

Von  Behring's  Suppression  of  Tuberculosis.     (Bolduan.)     {In  press.) 
Worcester  and  Atkinson.     Small  Hospitals,  Establishment  and  Maintenance, 
and  Suggestions  for  Hospital  Architecture,  with  Plans  for  a  Small 

Hospital i2mo,  i  25 

HEBREW  AND  CHALDEE   TEXT-BOOKS. 

Green's  Grammar  of  the  Hebrew  Language 8to,  3  00 

Elementary  Hebrew  Grammar i2mo,  i  25 

Hebrew  Chrestomathy Svo,  3  00 

Gesenius's  Hebrew  and  Choldee  Lexicon  to  the  Old  Testament  Scriptures. 

(Tregelles.) Small  4to,  half  morocco,  5  00 

Letteris's  Hebrew  Bible 8vo,  2  2 

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